Root doesn't matter at this point.
Short version: You can download the t0lte (t0lteatt is deprecated) OmniROM installer (and gapps, assuming you want them) to your phone's SD card, reboot to recovery and install both zip files, clear user data and reboot. First reboot will be a bit longer than usual. But I recommend you stick to the longer version below.
- Backup your apps using Titanium Backup.
- Download OmniROM, gapps and SuperSU to your phone's (internal or external) SD card.
- Download TWRP (Teamwin Recovery Project, a touchscreen interface recovery) zip file installer to your SD card. This will allow you to update OmniROM through their OpenDelta system, the ROM is able to automatically download small incremental update files for the latest nightly build, notify you that there's an update and install it in one click. (Put your gapps zip in the /sdcard/OpenDelta/FlashAfterUpdate folder. Mine also has the sensors fix, Xposed framework toggle and one or two other little mods.)
- Reboot to CWM recovery.
- Install the TWRP zip from SD card
- From CWM's advanced menu, reboot recovery. (Or reboot to CM, and recovery again.)
- From TWRP, make a full backup.
- Once that's done and you're back to the main menu, click "Install" and select the OmniROM zip.
- Add the gapps zip
- Add the SuperSU zip
- Slide to install
- Clear user data
- Proceed with activation, restore your apps and their data.
My phones: Galaxy Note II SGH-T889V (with LTE enabled
/ ext4 SD card support on TouchWiz ROMs
), Motorola XT-1045 Moto G LTE (TWRP
Previous phones: Nexus S GT-I9020A, Galaxy Gio GT-S5660M (Arpeggiomod ROM
/ Discussion, stock rooted ROM
), Motorola XT-1032 Moto G.
Phones for which I play "tech support" for family and friends: Galaxy Nexus GT-I9250, Galaxy Q SGH-T589R, Galaxy 551 GT-I5510M, LG C-800G Eclypse, Motorola XT-1032 Moto G