I am not sure if I completely understand your scenario.
However, I think it would be better if you implement your logic in the RoleProvider, instead of trying to change the user interface.
You could inherit the current RoleProvider (Telerik.DataAccess.AspnetProviders.TelerikProfileProvider) and override the appropriate methods (GetRoles, GetRolesForUser, etc.).
All the best,
the Telerik team