Take the checklist of actions and think about who does what? Then think about roles -- which actions are grouped to form roles? And positions -- how do positions and roles overlap (or not)? E.g., as a teacher, I have an institutional position that is material and ideological. Some roles are built into that position, others are assumed but can be removed or redistributed. The point is not to drop the roles or powers, but to redistribute them, to reconfigure the relationships.
How is protagonism a gathering of roles? What roles are needed to constitute protagonism?
See also Re-shuffling of Roles.