Role follows instruments until you set it yourself: Worship Leader ⇒ Leader; otherwise Member. Admin is separate.
Role starts from what someone does:
Picking the Leader role adds the Worship Leader position, and picking Member removes it, so the two normally agree.
If you set the role by hand it stays where you put it. Changing the instruments afterwards will not move it, and neither will saving the person again later. Whatever the Role buttons show is what is saved.