How to map roles

Hi everybody,
Does anybody succeed mapping roles from CAS to Pentaho?
I've configured Pentaho to use the authentication through CAS and is working properly. I also have some roles configured in Pentaho. So now is the moment to make CAS get thet roles from Active Directory and then map the roles to Pentaho.

Anybody could configure this? which tutorial have you followed?

Thank you so much in advance!