BuddyPress.org

Are you talking about groups in Buddypress? I can’t remember a bp-version where you were able to set user roles. Do you need a function to select different usertypes? If yes, there’s a solution – needs a few hacks in your template and also in buddypress core – but a needful tool.

Set up a wordpress-multisite installation, then hack the files. If you need help, just tell me.
Here’s the link:

http://cleverness.org/2010/08/08/add-user-types-to-wordpress-and-buddypress/