Role diversification, the different roles participants adopt within collaborative or inquiry-based teaching and learning environments, is insufficiently understood. We observed two inquiry classroom groups, two teachers and eight students, in weekly visits over three months. Qualitative analysis of audiorecorded interactions, interviews, journals, and fieldnotes generated frequencies, nature, and adaptability of student and teacher roles across the extended instructional units, and contextual variables including classroom context, teacher and student differences, and group-work dynamics. Just one role of the many was shared between teachers and students in the situations examined. Role diversification was supported as an indicator of collaborative-inquiry engagement having occurred.