Hi Catalin,

I have 2 suggestions.  If your roles are mutually exclusive, for example a user can belong to only role1 or role2, but not both roles, then you can just at 2 banner modules and in the module security specify that module 1 can only be viewed by role1, and module2 can only be viewed by role2. 

If that won't work, check out digRotate.  You can rotate content in the same module space.  You can limit content by role, and there is a banner tag you can use [ad:group:source(host or portal)] which will insert banners into your content rotation.  An added benefit with digRotate if you enable AJAX rotation, it will rotate your banners without having to refresh the browser.  See an example here.

Thanks,
Mike