The 3 Scrum Roles are:
- The Product Owner
- The Scrum Master
- The Development team
The various levels of services in the Scrum roles are:
- Scrum Master serves the Development Team
- Development Team serves the Product Owner
- Product Owner serves the stakeholders.
The accountability of the the various roles are:
- Product Owner is accountable for the value being delivered.
- Scrum Master is accountable for building High performing Scrum Teams by ruthlessly removing impediments and facilitating Development Team decisions. And the best way a Scrum Master can remove impediments is to empower/teach/coach the Development Team to remove them themselves. Only if the team is stuck the Scrum Master removes the impediments himself.
- Development Team manages itself and is accountable to build a releasable increment of software that adheres to their agreed 'Done' at the end of every sprint