The course being imported from (Course A) only has Teachers and Non-Editing Teachers assigned to it.
The course being imported to (Course B) only has that 1 Editing Teacher assigned to it.
The user is importing only content (activities), not users.
When they Perform the Import, the warning message displays for lots of other roles that no-one is assigned to on either course, e.g. Manager, and some custom ones that were created.
I'm just not sure why it's showing a warning for those at all.