Wikipedia:Rollback policy (failed proposal)

The rollback feature allows intentionally nonconstructive contributions to be reverted more quickly and more efficiently than with other methods. (User scripts have been written which mimic the functionality of rollback, but they merely hide details from the user, and are much less efficient, both in terms of bandwidth and time). Rollback links are displayed on page histories, user contributions pages, and diff pages.

Clicking on the link reverts to the previous edit not authored by the last editor. An automatic edit summary is provided and the edit is marked as minor. (An error message is returned if there is no last editor to revert to).

Rollback is currently available to administrators and any user may request that an administrator add the right to their account. Rollback should only be used to revert vandalism and should never be used to revert good faith edits or in content disputes. By requesting the permission, you agree to only use the tool for the accepted purpose; any misconduct with rollback will lead to its revocation.

Process
An editor who wants the tool should be known not to abuse rollback scripts or edit summaries.

Any editor in good standing may request the rollback feature from any administrator (administrators in Category:Wikipedia administrators willing to grant rollback requests have indicated a particular willingness to be approached). Alternatively, you may post a request at Requests for rollback.

An archive of some approved past requests is available at Requests for rollback/Approved; an archive of some failed requests is available at Requests for rollback/Denied; and the list of current rollbackers is available here.

Administrators
Administrators should check through each request and look for the user's ability to use the tool effectively. There are no prerequisites, but an administrator should look for experience in vandal fighting and signs of potential misuse (such as misuse of a script). If the administrator finds that the tool should be granted, they should go to Special:Userrights and add the rollback permission to the users account. The requests should be tagged with done or not done according to what the final decision is and bots will archive completed requests. If there is misuse of the tool, it should be revoked by the same method. Abuse should be reported to Administrators' noticeboard/Incidents.

From the Meta help page
On the user contributions page, admins have the additional "rollback" links at lines which are the last edit made by anybody to that article. Some user scripts (mentioned below) also give users the ability to rollback with an automated edit summary. The rollback link is also shown on the diff page when viewing the difference between any version of the page and the most recent one. Clicking on the link reverts to the previous edit not authored by the last editor, with an automatic edit summary of "Reverted edits by X (talk) to last version by Y," which marks the edit as "minor." If, between loading the User Contributions page and pressing "rollback," someone else edits or rolls back the page, or if there was no previous editor, you will get an error message.

The rollback link on the diff page is somewhat misleading because reversion is not necessarily to the old version shown (the diff page may show the combined result of edits including some by other editors, or only part of the edits the rollback button would revert). To see the changes the rollback button would revert, view the corresponding diff page.

Rollbacks should be used with caution and restraint, in part because they do not allow adding an explanation to the automatic edit summary. Reverting a good-faith edit may therefore send the message that "I think your edit was no better than vandalism and doesn't deserve even the courtesy of an explanation." It is a slap in the face to a good-faith editor. If you use the rollback feature for anything other than vandalism or for reverting yourself, it's polite to leave an explanation on the article talk page, or on the talk page of the user whose edit(s) you reverted.