Various kinds of applications have to be secure in an objectbased model. The secure system is required to not only protect objects from illegally manipulated but also prevent illegal information flow among objects. In this paper, we discuss how to resolve illegal information flow among objects in a role-based model. We define safe roles where no illegal information flow occurs. In addition, we discuss how to safely perform transactions with unsafe roles. We discuss an algorithm to check if illegal information flow occurs each time a method is performed.