Mutually-Inclusive Role Assignment

I don't know if anyone has had this requirement before or if there is even a way to do it, but I thought I would throw it out there.

What I am looking for is a way to assign 'mutually inclusive' role/security assignments within KM.

Here is the scenario.

- You have 2 roles: RoleA and RoleB

- I want to require that users be in BOTH RoleA and RoleB to get access to a KM folder.

- If a users is only in RoleA or only in RoleB they should not see the content.

Any ideas?