While some approaches to Agile are pretty specific about the roles, others are not so. Scrum is specific and, since it also very widely adopted, the Scrum roles have pretty much become the de-facto way of setting up a Team. In a Scrum Team, the roles are:

• Agile (Scrum) Team: a cross functional group of people who perform the actual work of problem solving, designing, verifying and documenting requirements and other changes. The Team includes the Product Owner and the Scrum Master. See What is the Role of the Team for more information.
• Product Owner: creates, prioritizes, and maintains the Product Backlog (the list of requirements for the product / project). See What is the Role of the Product Owner for more information.
• Scrum Master: a combination of facilitator, coach, fixer and gatekeeper for the Team. See What is the Role of the Scrum Master for more information.

Everyone else who has an interest in the work of the Team is considered a stakeholder. While that could be a lot of people, there are two roles that have a particular interest:

• Customers: represent the interests of the end users of the products developed (and may be internal or external).
• Management: represent the interests of the business or the organization.

See What is the Role of the Stakeholder for more information.

Do We Really Need a Full-time Product Owner or Scrum Master