An administrator creates role definitions for use in a workflow.
Workflow roles are not assigned permanently to users or groups. Instead, the participants associated with roles can change from one type of workflow to another, from one instance of a particular workflow to another, and even from one task of a workflow to the next.
We recommend that you create pairs of role definitions for use with workflow, one for an individual user assignment (Task Owner) and one for a pool assignment (Task Audience), such as for a parallel workflow step, or for posting to an audience where any audience member can accept the job. See The Difference Between a Task Audience and a Task Owner. Role definitions that are created for workflow typically do not have any capabilities assigned. This guards against inadvertently granting capabilities to users who participate in a workflow.
If your organization has already implemented workflow for some projects, your repository may contain role definitions that are suitable for a new workflow definition. Be sure to create all of the roles needed for the workflow, including the special roles for Status Changer, Task Owner, and Task Audience. See About Roles in Workflow.