What is the recommended approach to using Kentico user roles and authentication/authorization using Kentico 9, MVC stand alone application?
Is it possible to use the Kentico role attributes for controller methods?
What part of the API is used to authenticate and check authentication in this scenario?
It looks to me like this is not yet possible, and I am about to roll my own solution.
It`s not officially supported (yet). You can see list of supported and unsupported features (for new Kentico9 MVC) here. Of course you can still use Kentico API (Membership library) to make your own auth logic which fits your needs.