In my experience the best way is to create capability, and give administrators to administer that to appropriate users. 
I know that developer of "Custom certificate" used capability "edit_certificates" (I think), to determine who is a teacher in the course, but our Facilitators don't have that capability, and therefore they can not receive notification from this plugin.
There are much more other examples of mistakes made with "choosing capability to choose role", but I can't list them here, I need to make my self-enrolment block.
I know that developer of "Custom certificate" used capability "edit_certificates" (I think), to determine who is a teacher in the course, but our Facilitators don't have that capability, and therefore they can not receive notification from this plugin.
There are much more other examples of mistakes made with "choosing capability to choose role", but I can't list them here, I need to make my self-enrolment block.