Enterprises need to create and maintain the fit between their business processes and their business process support (BPS) systems. This frequently requires re-engineering of business processes. If the business processes design ration-ales are made explicit, the re-engineering of the existing business processes is easier. Making the design rationales ex-plicit is useful to understand why things exist as they are, and to understand if and how they can be changed. The most common way to capture design rationales is to list the design decisions underlying the business process. In the method proposed in this publication, we capture design rationales through role modeling. We document the design rationales for each role in the analyzed business process. The roles are described as the compositions of base func-tionalities. A base functionality is the specification of a role (or of a part of a role) from the viewpoint of one of the specific specialists who design the business process. These base functionalities are composed together to describe the roles of the participants to the business process. As a result, a business process modeler can understand who is respon-sible of what in the business processes. In collaboration with the specialists, the business modeler can then ensure that no important part of the business process is missing or is unnecessary. Thanks to this work, the business process can be verified before being automated with the BPS system.