Select which case and role to join, or create a new case for yourself. If you do not select a case and role to join, you will be automatically assigned to a case and role when the simulation begins.

Mockup below:

If no rows, display this text: "There are no cases yet."

After clicking join, redirect back to this page. Hide all buttons. Show new text at the bottom: "You are participating in this simulation as a player in case #X. The simulation will start XXX."

If casting type is group instead of open, do not display or group by the role column.