The three scrum roles are:
Product Owner: A product owner is actually the stakeholder of the project. He represents the project requirements before the team. He is responsible to have a vision of what to build and convey his detailed vision to the team. He is the starting point of an agile scrum software development project.
Development Team: Scrum team is formed by the collective contribution of individuals who perform for the accomplishment of a particular project. The team is bound to work for the timely delivery of the requested product.
Scrum Master: Scrum master is the leader and the coach for the scrum team who checks whether the scrum team is executing committed tasks properly. He is also responsible to increase the efficiency and productivity of the team so that they can achieve the sprint goal effectively.