Add selector for auth role

[arynh]

Is your feature request related to a problem? Please describe.
When directing the role from the state to the props of a components, we use selectors for pretty much all information except the auth role, which we reference directly.

Describe the solution you'd like
Sticking to the selector pattern for working with Redux state might make future things easier in the case that we start seeing more information derived from the state.

[arynh]

I'd like some input on this though because it might be entirely unnecessary.