Its simple really - there are only three:

Product Owner

The Product Owner is responsible for the visions, for getting value out of the investment.

The product Backlog is his anyone can put something on it but only the Product Owner can assign business value and change the order of the Backlog - the Team will make estimation on the costs.

The Product Owner is responsible for always having and updated and prioritized Backlog.

The Product Owner is responsible elaborate and give answers to any Items on the Backlog.

Teamet

The Team will be of four to eight memebers picked so that they have the necessary qualifications to solve the assignments.

The Team is responsible of solving the assignments, deliver the finished Items and commit to realistic Sprints.

It is the Teams responsibility to make realistic estimation of the Items on the Backlog.

The Team will report on  a daily basis to each other (and thereby to the rest of the organization) about the momentum of the Sprint.

The Team must be willing to take responsibility.

Scrum Master

The Scrum Master is passionate about achieving results through the peope in his Team.

The Scrum Master has the responsibility for the process he is in charge of the meetings and he sees to that the rules are followed.

The Scrum Master is responsible for the visibility and transparency of the process.

The Scrum Master is responsible for the Team starting to work and keep working in a cycle of constant improvement.