[Root]Root your XT925/XT926 running Jelly Bean
[INSERT TYPICAL DISCLAIMER]
I will not, can not, and shall not be held responsible for acts of durr. These instructions are fairly easy to follow and involve a little bit of android adb knowledge and a few fastboot commands. If you can not grasp them in about 30s reading, please, pay someone to perform this task for you and do NOT risk bricking your phone. Your warranty is now void, and all damage can, and may, be permanent. Thank you.
So, after fiddling around with trying to get the downgrade to ICS working, then rooting, then saving it up to JB, I said screw it and tried the method used on samsungs and it works. Lovely.
All you need, is...
1) Unlocked bootloader. If you don't have this, and aren't willing to have this, leave now.
2a) epinter's CWM recovery -- http://forum.xda-developers.com/show....php?t=1973904
2b) CWM / TWRP for the XT926 developer edition
3) Chainfire's SuperSU (Donate to this guy, he does a **** ton for the android community! ) -- http://download.chainfire.eu/298/SuperSU/
The process is SIMPLE.
Follow epinter's fastboot directions for installing cwm on your XT925 or the instructions for CWM/TWRP for the xt926 (Haven't tested, only have a 925) and from there, install the SuperSU package from your SD Card. Reboot, test, done.
As of time of writing, the current and 100% functional version of SuperSU is v0.99, I can not guarantee earlier version will work, however I assume that later ones will.