Hi Helen,
I'm on 3.4 and am having the same issue. My "Profile visible roles" are set to student and teacher only:
But the teacher sees other roles listed in the Participants List in two places:
Under the Roles column:
In the Filter:
they can also see the roles on the user profile:
For the Teacher Permissions, I have this set:
Any suggestions of what I may have mis-configured?
I've created tracker MDL-65030 to discuss the "Visible Roles" that are 'not' selected that are appearing in the Participants list or User Profiles for M 3.4, 3.5, and 3.6
The Moodle Docs don't provide any other details other than to select which roles you want to appear in those two places (https://docs.moodle.org/36/en/Site_security_settings#Profile_visible_roles)
It seems to be a bug to me that non selected roles are appears in those two places for non-admin users.