restoring course from a backup excludes most student roles

Hi,

I've noticed that when I restore a backed up course into Moodle 2, only some of the student user roles are restored along with the course content. Teacher roles seem to be restored. Just wondering if anyone else here has had a similar experience when restoring a backed up course into Moodle 2.

regards,
Cathal.

Waterford Institute of Technology,
Ireland