There was recently a discussion on the user list about what is possible with realm permissions.

https://groups.google.com/a/apereo.org/forum/#!topic/sakai-user/PdnDqtLte44

This lead me to search out and find some documentation that hasn't been updated since 2.4 related to what the various permissions in Sakai do and how this is setup. I think this would be great information to be updated and added to the online Admin guide rather than in this doc.

https://github.com/sakaiproject/sakai-reference/blob/master/docs/architecture/sakai_permissions.doc

This would give us a idea of what is currently possible as far as "read only" instructor as well as other roles that may be possible to create within Sakai.

The only other documentation I found out there was this one from udel where they try to map the permissions to the roles, but even this is out of date. I didn't see anything else.

http://www1.udel.edu/sakai/help/content/2.5.3-ud/sakai_permissions/armh.html