By default, some roles have the right to allow other roles to assign roles. For instance, a teacher is only allowed to assign Non-editing teacher, Student, and Guest roles, whereas the administrator is allowed to assign all roles except Authenticated user (because this is automatically assigned when a user signs in for the first time). There are instances when you either wish to change the default settings, for example, a teacher assigns roles to other teachers, or when newly created roles have to be managed. To achieve this, go to the Allow roles assignments tab in Users | Permissions | Define Roles in the Site Administration block:

In the screenshot, the modified allowances have been highlighted. Teachers are allowed to assign Teacher roles, and both...