diff --git a/rosidl_generator_py/resource/_msg.py.em b/rosidl_generator_py/resource/_msg.py.em
index 976aee32..f10ae370 100644
--- a/rosidl_generator_py/resource/_msg.py.em
+++ b/rosidl_generator_py/resource/_msg.py.em
@@ -22,6 +22,7 @@ from rosidl_parser.definition import FLOATING_POINT_TYPES
 from rosidl_parser.definition import INTEGER_TYPES
 from rosidl_parser.definition import NamespacedType
 from rosidl_parser.definition import SIGNED_INTEGER_TYPES
+from rosidl_parser.definition import UnboundedSequence
 from rosidl_parser.definition import UNSIGNED_INTEGER_TYPES
 }@
 @#<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
@@ -30,6 +31,9 @@ from rosidl_parser.definition import UNSIGNED_INTEGER_TYPES
 from collections import OrderedDict
 import numpy
 imports = OrderedDict()
+if message.structure.members:
+    imports.setdefault(
+        'import rosidl_parser.definition', [])  # used for SLOT_TYPES
 for member in message.structure.members:
     if (
         isinstance(member.type, AbstractNestedType) and
@@ -65,7 +69,7 @@ for member in message.structure.members:
 @(import_statement)@
 @[        if import_statement not in import_statements]@
 @{import_statements.add(import_statement)}@
-  # noqa: E402@
+  # noqa: E402, I100@
 @[        end if]
 @[    end for]@
 @[end if]@
@@ -227,6 +231,39 @@ string@
 @[end for]@
     }
 
+    SLOT_TYPES = (
+@[for member in message.structure.members]@
+@{
+type_ = member.type
+if isinstance(type_, AbstractNestedType):
+    type_ = type_.value_type
+}@
+        @
+@[  if isinstance(member.type, AbstractNestedType)]@
+@(member.type.__class__.__module__).@(member.type.__class__.__name__)(@
+@[  end if]@
+@# the typename of the non-nested type or the nested value_type
+@(type_.__class__.__module__).@(type_.__class__.__name__)(@
+@[  if isinstance(type_, BasicType)]@
+'@(type_.typename)'@
+@[  elif isinstance(type_, AbstractGenericString) and type_.has_maximum_size()]@
+@(type_.maximum_size)@
+@[  elif isinstance(type_, NamespacedType)]@
+[@(', '.join("'%s'" % n for n in type_.namespaces))], '@(type_.name)'@
+@[  end if]@
+)@
+@[  if isinstance(member.type, Array)]@
+, @(member.type.size)@
+@[  elif isinstance(member.type, BoundedSequence)]@
+, @(member.type.maximum_size)@
+@[  end if]@
+@[  if isinstance(member.type, AbstractNestedType)]@
+)@
+@[  end if]@
+,  # noqa: E501
+@[end for]@
+    )
+
     def __init__(self, **kwargs):
         assert all('_' + key in self.__slots__ for key in kwargs.keys()), \
             'Invalid arguments passed to constructor: %s' % \
diff --git a/rosidl_generator_py/test/test_interfaces.py b/rosidl_generator_py/test/test_interfaces.py
index e4a7cf59..6c4f23e0 100644
--- a/rosidl_generator_py/test/test_interfaces.py
+++ b/rosidl_generator_py/test/test_interfaces.py
@@ -16,6 +16,7 @@
 
 import numpy
 import pytest
+
 from rosidl_generator_py.msg import Constants
 from rosidl_generator_py.msg import Nested
 from rosidl_generator_py.msg import Primitives
@@ -24,6 +25,13 @@
 from rosidl_generator_py.msg import Various
 from rosidl_generator_py.msg import WStrings
 
+from rosidl_parser.definition import Array
+from rosidl_parser.definition import BoundedSequence
+from rosidl_parser.definition import BoundedString
+from rosidl_parser.definition import NamespacedType
+from rosidl_parser.definition import UnboundedSequence
+from rosidl_parser.definition import UnboundedString
+
 
 def test_strings():
     a = Strings()
@@ -314,7 +322,7 @@ def test_slot_attributes():
         assert expected_slot_type == nested_slot_types_dict[expected_field]
 
 
-def test_primative_slot_attributes():
+def test_string_slot_attributes():
     b = StringArrays()
     assert hasattr(b, 'get_fields_and_field_types')
     assert hasattr(b, '__slots__')
@@ -349,3 +357,63 @@ def test_modifying_slot_fields_and_types():
     string_slot_types_dict_len = len(string_slot_types_dict)
     string_slot_types_dict[1] = 2
     assert len(getattr(b, 'get_fields_and_field_types')()) == string_slot_types_dict_len
+
+
+def test_slot_types():
+    a = Nested()
+    assert hasattr(a, 'SLOT_TYPES')
+    assert hasattr(a, '__slots__')
+    nested_slot_types = Nested.SLOT_TYPES
+    nested_slots = getattr(a, '__slots__')
+    assert len(nested_slot_types) == len(nested_slots)
+    assert isinstance(nested_slot_types[0], NamespacedType)
+    assert nested_slot_types[0].namespaces == ['rosidl_generator_py', 'msg']
+    assert nested_slot_types[0].name == 'Primitives'
+
+    assert isinstance(nested_slot_types[1], Array)
+    assert isinstance(nested_slot_types[1].value_type, NamespacedType)
+    assert nested_slot_types[1].value_type.namespaces == \
+        ['rosidl_generator_py', 'msg']
+    assert nested_slot_types[1].value_type.name == 'Primitives'
+
+    assert isinstance(nested_slot_types[2], BoundedSequence)
+    assert isinstance(nested_slot_types[2].value_type, NamespacedType)
+    assert nested_slot_types[2].value_type.namespaces == \
+        ['rosidl_generator_py', 'msg']
+    assert nested_slot_types[2].value_type.name == 'Primitives'
+
+    assert isinstance(nested_slot_types[3], UnboundedSequence)
+    assert isinstance(nested_slot_types[3].value_type, NamespacedType)
+    assert nested_slot_types[3].value_type.namespaces == \
+        ['rosidl_generator_py', 'msg']
+    assert nested_slot_types[3].value_type.name == 'Primitives'
+
+
+def test_string_slot_types():
+    b = StringArrays()
+    assert hasattr(b, 'SLOT_TYPES')
+    assert hasattr(b, '__slots__')
+    string_slot_types = StringArrays.SLOT_TYPES
+    string_slots = getattr(b, '__slots__')
+    assert len(string_slot_types) == len(string_slots)
+
+    assert isinstance(string_slot_types[0], Array)
+    assert isinstance(string_slot_types[0].value_type, BoundedString)
+    assert string_slot_types[0].size == 3
+    assert string_slot_types[0].value_type.maximum_size == 5
+
+    assert isinstance(string_slot_types[1], BoundedSequence)
+    assert isinstance(string_slot_types[1].value_type, BoundedString)
+    assert string_slot_types[1].maximum_size == 10
+    assert string_slot_types[1].value_type.maximum_size == 5
+
+    assert isinstance(string_slot_types[2], UnboundedSequence)
+    assert isinstance(string_slot_types[2].value_type, BoundedString)
+    assert string_slot_types[2].value_type.maximum_size == 5
+
+    assert isinstance(string_slot_types[3], UnboundedSequence)
+    assert isinstance(string_slot_types[3].value_type, UnboundedString)
+
+    assert isinstance(string_slot_types[4], Array)
+    assert isinstance(string_slot_types[4].value_type, UnboundedString)
+    assert string_slot_types[4].size == 3
diff --git a/rosidl_runtime_py/package.xml b/rosidl_runtime_py/package.xml
index 9139c9a7..2de8eb66 100644
--- a/rosidl_runtime_py/package.xml
+++ b/rosidl_runtime_py/package.xml
@@ -11,6 +11,7 @@
 
   <exec_depend>python3-numpy</exec_depend>
   <exec_depend>python3-yaml</exec_depend>
+  <exec_depend>rosidl_parser</exec_depend>
 
   <test_depend>ament_copyright</test_depend>
   <test_depend>ament_flake8</test_depend>
diff --git a/rosidl_runtime_py/rosidl_runtime_py/__init__.py b/rosidl_runtime_py/rosidl_runtime_py/__init__.py
index 5f40b2ed..7a71aa92 100644
--- a/rosidl_runtime_py/rosidl_runtime_py/__init__.py
+++ b/rosidl_runtime_py/rosidl_runtime_py/__init__.py
@@ -12,13 +12,17 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from .convert import get_message_slot_types
 from .convert import message_to_csv
 from .convert import message_to_ordereddict
 from .convert import message_to_yaml
+from .import_message import import_message_from_namespaced_type
 from .set_message import set_message_fields
 
 
 __all__ = [
+    'get_message_slot_types',
+    'import_message_from_namespaced_type',
     'message_to_csv',
     'message_to_ordereddict',
     'message_to_yaml',
diff --git a/rosidl_runtime_py/rosidl_runtime_py/convert.py b/rosidl_runtime_py/rosidl_runtime_py/convert.py
index fc783f13..1babe73c 100644
--- a/rosidl_runtime_py/rosidl_runtime_py/convert.py
+++ b/rosidl_runtime_py/rosidl_runtime_py/convert.py
@@ -154,3 +154,13 @@ def _convert_value(value, truncate_length=None):
         # Assuming value is a message since it is neither a collection nor a primitive type
         value = message_to_ordereddict(value, truncate_length=truncate_length)
     return value
+
+
+def get_message_slot_types(msg: Any) -> OrderedDict:
+    """
+    Return an OrderedDict of the slot types of a message.
+
+    :param msg: The ROS message to get members types from.
+    :returns: An OrderedDict with message member names as keys and slot types as values.
+    """
+    return OrderedDict(zip([s[1:] for s in msg.__slots__], msg.SLOT_TYPES))
diff --git a/rosidl_runtime_py/rosidl_runtime_py/import_message.py b/rosidl_runtime_py/rosidl_runtime_py/import_message.py
new file mode 100644
index 00000000..ceb11ad8
--- /dev/null
+++ b/rosidl_runtime_py/rosidl_runtime_py/import_message.py
@@ -0,0 +1,24 @@
+# Copyright 2019 Mikael Arguedas.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import importlib
+from typing import Any
+
+from rosidl_parser.definition import NamespacedType
+
+
+def import_message_from_namespaced_type(message_type: NamespacedType) -> Any:
+    module = importlib.import_module(
+        '.'.join(message_type.value_type.namespaces))
+    return getattr(module, message_type.value_type.name)
diff --git a/rosidl_runtime_py/rosidl_runtime_py/set_message.py b/rosidl_runtime_py/rosidl_runtime_py/set_message.py
index cfb36563..d84a7a4d 100644
--- a/rosidl_runtime_py/rosidl_runtime_py/set_message.py
+++ b/rosidl_runtime_py/rosidl_runtime_py/set_message.py
@@ -15,6 +15,11 @@
 from typing import Any
 from typing import Dict
 
+from rosidl_parser.definition import AbstractNestedType
+from rosidl_parser.definition import NamespacedType
+from rosidl_runtime_py.convert import get_message_slot_types
+from rosidl_runtime_py.import_message import import_message_from_namespaced_type
+
 
 def set_message_fields(msg: Any, values: Dict[str, str]) -> None:
     """
@@ -33,4 +38,13 @@ def set_message_fields(msg: Any, values: Dict[str, str]) -> None:
         except TypeError:
             value = field_type()
             set_message_fields(value, field_value)
+        rosidl_type = get_message_slot_types(msg)[field_name]
+        # Check if field is an array of ROS messages
+        if isinstance(rosidl_type, AbstractNestedType):
+            if isinstance(rosidl_type.value_type, NamespacedType):
+                field_elem_type = import_message_from_namespaced_type(rosidl_type)
+                for n in range(len(value)):
+                    submsg = field_elem_type()
+                    set_message_fields(submsg, value[n])
+                    value[n] = submsg
         setattr(msg, field_name, value)
diff --git a/rosidl_runtime_py/test/rosidl_runtime_py/test_set_message.py b/rosidl_runtime_py/test/rosidl_runtime_py/test_set_message.py
index a74a6d92..4f178d65 100644
--- a/rosidl_runtime_py/test/rosidl_runtime_py/test_set_message.py
+++ b/rosidl_runtime_py/test/rosidl_runtime_py/test_set_message.py
@@ -91,3 +91,39 @@ def test_set_message_fields_invalid():
     invalid_type['int32_value'] = 'this is not an integer'
     with pytest.raises(ValueError):
         set_message_fields(msg, invalid_type)
+
+
+def test_set_nested_namespaced_fields():
+    unbounded_sequence_msg = message_fixtures.get_msg_unbounded_sequences()[1]
+    test_values = {
+        'basic_types_values': [
+            {'float64_value': 42.42, 'int8_value': 42},
+            {'float64_value': 11.11, 'int8_value': 11}
+        ]
+    }
+    set_message_fields(unbounded_sequence_msg, test_values)
+    assert unbounded_sequence_msg.basic_types_values[0].float64_value == 42.42
+    assert unbounded_sequence_msg.basic_types_values[0].int8_value == 42
+    assert unbounded_sequence_msg.basic_types_values[0].uint8_value == 0
+    assert unbounded_sequence_msg.basic_types_values[1].float64_value == 11.11
+    assert unbounded_sequence_msg.basic_types_values[1].int8_value == 11
+    assert unbounded_sequence_msg.basic_types_values[1].uint8_value == 0
+
+    arrays_msg = message_fixtures.get_msg_arrays()[0]
+    test_values = {
+        'basic_types_values': [
+            {'float64_value': 42.42, 'int8_value': 42},
+            {'float64_value': 11.11, 'int8_value': 11},
+            {'float64_value': 22.22, 'int8_value': 22},
+        ]
+    }
+    set_message_fields(arrays_msg, test_values)
+    assert arrays_msg.basic_types_values[0].float64_value == 42.42
+    assert arrays_msg.basic_types_values[0].int8_value == 42
+    assert arrays_msg.basic_types_values[0].uint8_value == 0
+    assert arrays_msg.basic_types_values[1].float64_value == 11.11
+    assert arrays_msg.basic_types_values[1].int8_value == 11
+    assert arrays_msg.basic_types_values[1].uint8_value == 0
+    assert arrays_msg.basic_types_values[2].float64_value == 22.22
+    assert arrays_msg.basic_types_values[2].int8_value == 22
+    assert arrays_msg.basic_types_values[2].uint8_value == 0