Or try http://wordpress.org/extend/plugins/user-role-editor/ ... It is said to be WP3+ Multi Site compatible and not as complicated as Role Scoper. In fact, it's more like Capability Manager which actually approaches the role and capabilities management from a completely different angle that Role Scoper. It might even be used in conjunction with Role Scoper.
Testing it right now and all seems to work... So if Capability Manager would fit your needs (if it worked) and Role Scoper provides just too much (complicating things) then you might find User Role Editor will do the job on WPMS :)