There are three roles on a Scrum Team, no more and no less. These roles are: ScrumMaster, Product Owner, and the Team Members. It is critical to have all three roles present on the Scrum Team to get all needed responsibilities taken care of in an effective way. The Product Owner is responsible for the product and how the team connects with that product. The ScrumMaster is responsible for improving the use of Scrum in the organization and team, as well as removing any obstacles that slow the team down. The Team Members are responsible for getting the work done by self-organizing and finding ways to improve their own process and work. Without one of these key roles, the team would be missing a key focus and job. As well, Scrum specifically disallows any other roles on the Scrum Team. A person who has an official role of Tester cannot be on a Scrum Team. However, the same person, if given the official role of Team Member can be on a Scrum Team. If people have their official titles, performance evaluations etc. done in their traditional roles, it hinders self-organizing and causes conflicts of interest. A team is not a Scrum Team until those old roles are eliminated.