Android 5.1.1 update for OnePlus One as CM12.1 was just released by the OnePlus One team. If you upgraded your OnePlus One to Android 5.1, you may looking to root it now. Well, that’s super easy. To root OnePlus One on CM12.1 Android 5.1 update, just install the TWRP recovery and then flash SuperSU root package.
To install TWRP, you will need to have unlocked bootloader. To help you with unlocking bootloader (if not done already), and install TWRP, there is a good all-in-one utility available in the form of a toolkit here.
If this is your first time, then it may take you some time. But given that you own OnePlus One, you most probably are already master of flashing TWRP and rooting a device using SuperSU. No?
Do let us know if you need any help over this. Use comments section below for faster help from us.