I have seen first rollback awarded to few users in TSE, I just want to know that:
How do they normally achieve that?
The corresponding badge Cleanup is given to users who have used the roll back option for the first time. What is roll back? Well, if you check the edit history of a post, you will note a set of links next to each version:
link on all versions and
rollback on all but the final one.
source will give you the raw input of any past version.
edit will allow you to edit it and save the edits as the current version of the post.
link provides a convenient way to link to old versions of a post and
rollback re-saves an old version of the post, overwriting any changes that have happened since.
Every time a user uses said
rollback option the first time, they are awarded the cleanup badge.