I want to upgrade my Galaxy S II to Android 2.3.5, and my provider only has 2.3.3. So I have to use a ROM from samfirmware.com. Do I have to SIM unlock my phone before installing one of these ROMs? Do I have to root it?
The Galaxy S2 has an unlocked bootloader, which means you can install any rom on it, rooting is not mandatory, some roms have root privileges, some don't.