I want to reverse the changes from one of my checkins. In the right-click context menu of the particular changelist, there are these two options:
What is the difference between these two? In what situations should I use either one?
Rollback... will prompt you to select a folder to rollback, ie, it will work on specific folders, and you can rollback to labels or changlists or dates. Back out works on the files in specific changelists.
Both of these operations restore a set of files to a previous state and are essentially faster, safer ways of undoing mistakes than using the p4 obliterate command (and you don't need admin access to use them). In the case of "Rollback...", this could be any number of files, even an entire depot. You can tell it to rollback to a specific revision, changelist, or label. In the case of "Back Out Submitted Changelist #####", the restore operation is restricted to the files that were submitted in changelist #####. Those files are restored to the state they were in before you submitted that changelist.
Both operations work by essentially submitting old revisions as new revisions. Suppose you have a file that has been changed three times, so it's current revision is #3. If you roll this file back to revision #2, Perforce will check this file out, revert it's contents to the state that it was in as of revision #2, then submit the file. This file will now have four revisions, revisions #4 and #2 being the same.