I need to ask about ROM installation on my android, samsung galaxy s2.

i wanted to know weather you HAVE to root your android device (in my case, a samsung galaxy s2) to install another ROM. and also if I do end up installing a ROM, after the installation, would I have lost all my apps that I previously downloaded? or would they be there? thanks :)
Asked Jul 21, 2012

TIP: If it's not your answer to this question, please click "Leave a Comment" button under the question to communicate with the question owner.