This study investigated how different co-design partners engaged in the co-design process while developing two epistemic game scenarios designed to support professional identity development in teacher education. Using a participatory design research framework, the study examined the co-design process of these two game scenarios. Data were collected through semi-structured interviews, online video recordings of co-design sessions and whole-class discussions, open-ended questionnaires, and researcher field notes. Reflexive thematic analysis was used for data analysis, and convenience and purposeful sampling methods were employed for participant recruitment. Findings highlight that the co-design process provides significant learning opportunities for all team members by breaking down traditional roles, fostering collaborative and mutual learning, and integrating diverse stakeholder perspectives. Pre-service teachers primarily took on ‘user’ and ‘tester’ roles, while teacher educators and in-service teachers assumed ‘informant’ roles. Although participants’ roles evolved and diversified throughout the co-design process, deeper engagement should be actively facilitated to ensure a more effective co-design experience.