cancan and authorization on controller actions of a gem.

Hello. I've installed cancan and bigbluebutton_rails, https://github.com/mconf/bigbluebutton_rails. The gem bigbluebutton_rails has some models and controllers, for example has bigbluebutton/servers_controller.rb. This controller has some actions like create, join, authorize, etc. I want that only users with role admin can create. What can I do? I need to put load_resource in bigbluebutton/servers_controller.rb? But it is inside a gem and I think it is not recommended to modify gems code.