Can OP rollback the post if OP strongly feel rightly to do so? Is there a punishment for OP if he/she rollback his/her post?
You can rollback a post, but please realize that Stack Exchange is collaboratively edited: people can and will edit your posts to improve them and make them better comply with our rules and guidelines. If you're not comfortable with people editing your stuff in good faith, this might not be the site for you.
Rollbacks should only be used when edits are done in bad faith (e.g. vandalism) or if the edits drastically change the meaning of your post without explanation. Otherwise, please try to resolve any issues in comments before resorting to a rollback: we will lock posts that devolve into edit warring.
Usually there's no punishment. However, it all depends on why and how often you roll back edits.
All posts to Stack Exchange are made under the cc-by-sa 3.0 license that means that other people can edit "your" stuff" so if someone spots something they consider wrong in your post, they are able and, indeed encouraged, to correct it.
However, people should exercise caution over edits - especially to questions - that might change the meaning of the post. If you think this has happened then roll back explaining why. You might also want to double check your post for spelling and grammatical errors and check the formatting. These could be why someone started editing your post in the first place.
What's not welcome is where two (or more) users engage in edit wars, rolling back each others edits. You also shouldn't roll back the automatically inserted text that gets inserted when a post is closed as a duplicate.
If you think someone has maliciously edited one of your posts either flag it or raise it here on meta.