Please see the rollback thread here, or in its archives, later on:
Rollback removes material without a meaningful edit summary. This often looks like vandalism to others. It can severely mess up the flow of talk pages. It can discourage and baffle editors, especially newer ones. If these editors try to repair this "vandalism" they are quickly reverted, often again without a meaningful edit summary. Or with some very cryptic edit summary full of acronyms like "LTA".
This can drive away some editors, and Wikimedia needs every single one to revert the decline of editors in some wikis. See active editor statistics:
Need some plain English edit summaries that are actuated by default. Via the rollback link, or via a new "Rapid Undo" link to the right of the Undo link on diff pages. Developers can decide.
Nothing between clicking the rollback button and the actual revert. The rollback function could use the last used edit summary. Without any confirmation clicks. The editor can pick another default edit summary from a list at any time. That default list would be in plain English, and would be built in to Wikimedia.
That list also could have a section for adding more edit summaries by the editor.
The latest chosen edit summary should be clearly visible on the diff page or revision history page. So that the editor knows what will show up as the edit summary upon clicking the rollback button.