Rails with Angular and Devise

I had a non-Angular Rails app with Devise powering the authentication.
Almost all of it.

However as we are moving it to AngularJS, had a question or two about
to integrate that with Angular.

  1. What all parts of Devise can still be used?
  2. What are best practices around how to maintain session in angular?
  3. Also, how do I manage multiple roles(based on 2 different
    both devise authenticable) ?