Rollbacks have a specified job of undoing unconstructive edits consisting of spam/vandalism. They are second in command after the acme heads. Rollbacks don't have to be active all the time, so its a good position if you are a random contributor to the wiki.
Who are the wiki's rollbacks?
Note: It is important to know that wizards and acme heads have rollback rights by default. When promoting a rollback to a head please remove their rollback right.