Nowadays, virtual enterprise, extended enterprise, wide supply chain and enterprise network are organizational structures recognized by the scientific and professional communities. The challenges in the engineering of these systems consist in proposing solutions that take into account both the social and the technical aspects simultaneously. The modelling approach and the models are components of the system engineering framework [GERAM 1999]. This paper proposes a role based and process based modelling approach for organization networks. This approach uses a combination of the role based modelling approach and the process based modelling approach. This paper shows the importance of the role concept and proposes new definitions.