We've added the ability to view user role changes in your workspace via the Activity Feed. When a user is added or removed from your workspace, or their role level is changed, entries will now be reflected in the workspace's Activity Feed showing who made the change, what user was changed, and the roles that changed.
Note that when a user's role is changed, there will be an entry showing the new role being added and the previous role being removed, as shown below.
Activity Feed entries will be available for all role changes made subsequent to this feature release, but not for historic role changes that predate the release.