Role Extensions, when configured, allows you to make automatic workflow transitions. For each workflow, you can configure:
These automatically assign tasks inside a component (standard JIRA issues) based on component roles. For instance, you may define that the leader of a component is the auto-assignee of tasks inside it.
These concern workflow steps (transitions). You can set that a given workflow step can only be performed by user with a certain role for this component, for instance that only the reviewer can close an issue.
They verifiy if inside a workflow step transition the task was indeed assigned to the user who should have this task assigned according to defined component roles
Open the administration of your JIRA project, then click on Workflows. Hit Edit next to a Workflow, and then click the name of any transition. Now you can go to any of the tabs mentioned above and select the plugin's entry: