it works just the same in mojoportal, it will use mojoportal roles.
only detail to understand is if you look in the mp_Roles table you will see roles have rolename and displayname, rolename never changes, edits only affect displayname. you must use rolename not displayname in web.config
so for example Administrators is displayname, but the real role name is Admins and that is what must be used form web.config