on Respecting (Drupal) Roles

I'm looking for a way to have phpbb respect a particular user role when users in that role log into the forum.

On a project I'm working on I'm using Ubercart to give members who pay a special role (Membership). (And when their subscription is over they revert to regular authenticated users.) Naturally, I would like to give them private forums, too. Although I could use phpbb3 as a general message board and then use the built-in Drupal forums as a Membership board, I'd rather keep it all in phpbb3.

So if Drupal's Membership group is given the id of 4 and phpbb's Membership group has the id of 8 is there a way for Drupal to tell phpbb that a user is in that group and give it all the permissions such a group has? (private forums, special user-online color, all those users in "Membership" lists, special group avatars, larger PM limits, etc.) And when that user's subscription expires, they're put back into the registered users group?

~silverwing