Perhaps it might be worth considering providing optional views of the Participants page that allow for quick selection.

Example:
Add a link in the Roles column header. This takes the user to a dedicated screen for managing the roles of users enrolled in the course. This separate screen lists the enrolled users on the left, and columns for each role available in the course. In each column there is a multiple select checkbox for that role for that user.

The user can then see at a glance which roles are currently applied to which enrollees and can then quickly add or remove roles by selecting the relevant check box.

An option at the top of each column would allow selecting all checkboxes in that column. If some enrollees then don't need to be given that role, the relevant checkbox can be deselected

A 'Save; button is provided at the bottom of the screen.

Additionally, the list of users shown in this selection screen could be customised by applying a filter when searching for users on the main screen. That is, the user would filter the users in the main Participants screen, and then this filtered list would be passed through to this selection screen.

Separate screens like this could feasibly be provided for Role, Groups and Status columns in the main Participants view.

Thanks.