The Activity Roster will display all students that have enrolled. There is an Enrollment Status column that displays if that enrollment is Approved or Deleted. The Deleted enrollments reflect students that have been detached from the activity. This allows you to view all enrollment actions related to that activity and provides a more complete picture of what occurred with all of the enrollments for it.
If you need to remove students from the Roster that have been detached, you can download the Roster to Excel or another spreadsheet program, sort that column and remove any Deleted from the Roster. That data can then be saved, emailed and/or printed as needed.