The Rational Unified Process emphasizes the adoption of many best practices of modern software development, as a way to reduce the risk inherent in developing software. Three important characteristics such as use-case driven, architecture centric and iterative and incremental approaches make it a unique process that can guide software teams in the development of complex software systems in the fastest way.  The current approach used to model visually the Rational Unified Process is by using mostly activity diagrams, which prove to be deficient in expressing a unified view of roles, activities and artifacts in the same diagram.  We propose the use of Role Activity Diagrams (RAD), and our own extended version, XRAD, for Business Modeling, Requirements, Analysis and Design, Implementation, Test, and Deployment disciplines, as elements of originality of this thesis. We demonstrate through examples that XRAD process modeling result in superior expressive power when compared to the other diagrams that are available in the literature