In 1.9 we only had "Course participants" and role assignments page. The course participants was designed both for normal users and for enrolment related tasks, unfortunately the complexity of the code is getting too big there.
Solution was to add a separate enrolment only page accessible via the "Course administration" section in navigation. Each enrol instance may add sub pages with some enrolment details.
This page handles:
1/ list of all enrolled users with filtering by enrol instance, sorting, etc.
3/ view, add and remove roles
4/ view add and remove groups
5/ link to enrol users pages or in future enrol user ajax interface
Access controlled by moodle/course:enrolreview and other standard capabilities for role and group management.