I think it will be nice to have a simple roles management.
Suggestion:
We can add a new constructor with an array of roles as extra parameters. By default, if nothing is provided (actual case) a user has all roles.
When the file manager start, it does an extra request to get the user roles to the connector. (It does not seem too hard to implement because the logic is already implemented with the "has_capability" functions.)
This will real plus in a CMS usage or when you have different profiles of users that use the file manager in your app.