We try to document all new user roles in the Release Notes with explanations around them. Those items are usually marked with "Pre-work Needed" so you could quickly scan the release notes to find them or search for "[". PQM was released in 6.1.1 and it included a lot of new roles. PQM roles are documented in the Admin guide.
If you want a faster and more accurate way to compare you can get a quick list of all of the roles available by just looking at the roles table in the database and comparing that to your previous version. "select * from Roles"
Hope this helps