In order for instructors to view the roster, they'll need one of two permission sets assigned to them:
Option 1:
"Can view users" and
"Can view reservations"
These permissions allow your instructors to see the roster but not make edits. Just so you know, instructors will see all rosters and reservations, not just their own classes.
Option 2:
"Can view instructing classes"
"Can view users"
This will allow instructors to only view the roster for classes that they are teaching but not see the roster for any other classes. Instructors will also be able to view users' profiles belonging to locations they have access to.
It's likely that your instructors only have the "Can instruct classes" permission. If you'd like to add additional permissions, you can click here to submit a change request.