In business analysis roles and individuals are two different things.
An individual can have many different roles. This is true in personal life as well as in business. On the personal side, you can fulfill a parenting role, a friend role, etcetera. In the business world, you can have a position that requires you to meet many different roles.
Many different individuals can also fulfill a single role.
A customer experience role, or the role of managing and maintaining a large asset may be fulfilled by many different individuals.
Understanding roles is one way of understanding a business at a higher level.