Can I root SGSII, edit/modify it and unroot it?

[bostjan]

I use unrooted Galaxy SII. My carrier in EU adjusted/modified the ICS in the way that when the screen is locked there is a sentence on it saying ?Swipe to unlock?. I asked the carrier how can I remove that and it told me that I cannot (I need to root it, and then I can).

So, I would like to root the phone, remove the sign and unroot it (deroot ). I don?t want to have rooted phone.

Any suggestions? Help?

Thank you.