Our research aims at understanding the various forms of participation in Open Source Software (OSS) design, seen as distributed design in online spaces of actions - discussion, implementation and boundary between these spaces. We propose a methodology - based on situated analyses of a formal design process used in the Python project- to identify the distribution of actual roles (implementation, interactive, group and design oriented) performed by participants into and between the spaces (defining boundary spaces). This notion of roles is grounded in collaborative design activities performed online by participants. This way, our findings complete the core-periphery model of participation in OSS. Concerning the distribution of roles between spaces, we reveal a map of participation in OSS: the majority of participants are pure discussants but all participants in the implementation spaces do also act in the discussion space and only few participants act at boundary spaces. Concerning the distribution of roles between participants in the discussion space, we reveal that interactions are structured by a central hub (occupied by key-participants) and that, whereas design-oriented roles are spread among all participants, group-oriented roles are performed by one or two participants in the respective spaces and at their boundary. Finally, combination of roles reveals five individual profiles performed by participants. Our approach could be extended to other design situations to explore relationships between forms of participation- in particular those revealing use-oriented contributions- performance, and quality of the design product. Finally, it could be a basis for specifying tools to monitor and manage community activity for both research issues and support of online community.