What is a 'rollback'?
I don't understand meaning of first roll back badges. When I move cursor on CleanUp badge it
shows message "First Rollback". What the meaning of this? is we done some action and again
Rolling back a post means that you return it to a previous version.
If there were some edits made to add information to a post that after some clarification are not needed, instead of editing the post again to remove the added information, one could simply "roll back" the post to a previous version.
When you are viewing the edit history of a post, you can see the "rollback" link as shown in the screenshot below.
That is pretty much the explanation of what a rollback is. With regard to how to earn the "clean up" badge, you can see the possible duplicate link at the top of your post or inspect @alphamale's answer.
Rollback is happened when somebody or you edits your post and you discard that change and roll it back to its previous state. It also remove any offensive flags that have been set on a question.
You can refer to this question:
Hope this helps.
For rollback first click on the edited as i circled it in image
Then click on rollback