Online epistemic communities, whose aim is the co-elaboration of a knowledge object, have been studied recently using mostly social network analysis and qualitative interview techniques. Whilst these approaches can enable understanding of who communicates with whom most frequently, they lack explanatory power with respect to the collaborative process itself, in particular concerning identification of effective interactive roles. We propose a socio-epistemic approach to analysing such communities, based on qualitative analysis along epistemic and dialogical dimensions, combined with quantitative (statistical) techniques . This approach, elaborated to understand various forms of designers’ participation in an architectural design meeting, has been further developed to study roles in online OSS design communities and Wikipedia. In this paper, the method is illustrated with respect to a debate in the French-speaking astronomy Wikipedia community. We conclude with perspectives for further research, including visualisation of the dynamic interplay between roles, and use of NLP techniques for analysing argumentation.