Root on Lollipop custom ROMs?

Hi,

I've been fiddling around with Lollipop for the Z2 device today and I've got a question.

Are 5.1.1 based custom ROMs root-possible? I've first managed to make a stock pre-rooted 5.1.1 .ftf and everything was fine, both root and recovery, but my phone was overheating like crazy on it so I decided to try a custom ROM, Paranoid Android to be exact. I got the latest stable from their site and almost successfully installed it using the TWRP. Almost, because I forgot to re-flash the recovery. Then it turned out I can't root it and couldn't find a way to do so. I've since gone back to 4.4.2 using Flashtool, rooted it and installed the XZDualRecovery.

So, my question(s) is/are, what did I do wrong? Would flashing the flashable XZDualRecovery after the custom ROM and gapps sufficied? Or maybe flashing the SuperSU package? Or maybe, is it impossible to have a rooted custom ROM on 5.1.1? And if isn't, I'd be really grateful if someone supplied me with a hint or something, because I don't want to go through all the trouble only to downgrade again.

I'm using this for recovery : http://forum.xda-developers.com/show....php?t=2785598
And used this guide for the prerooted .ftf, though I guess it's not related at all to my questions, except the SuperSU package I'm thinking of using: http://forum.xda-developers.com/xper...ckage-t2933155

Thanks in advance.