Scrum has 3 roles: Product Owner, ScrumMaster and Team. I learned this from Ken and Jeff in Trainings and by reading their books. But if you have a closer look and if you hear the discussion than it becomes obvious that everybody talks about: Customer, End User and Management. If you think some time about this, you find that these three roles have distinct responsibilities in Scrum: The End User has to define what he wants, and accept it, the Customer has to pay for the delivered product and Management provide the organizational support for the Scrum.Teams.
I agree with Ken that the original three roles of Scrum are fundamental and that they construct the Scrum-Team. AND we need to start talking about the other three roles and we need to figure out, how they will contribute to a wider Scrum Framework.