Roles and permissions

Hi all, reading in the moodle forums I was able to solve a problem with users unable to read the news forum posts on the home page by assigning their homepage role to student, however something I'm encountering is that locked courses are not actually locked...

I entered the course editing menu and found that I had the default role as a student for this course, which I changed to "Authenticated User". I'm now trying to unenrol everyone from the course, but can't seem to do so.

Any ideas?