Chainfire has been pretty busy today. He earlier released root for several Nexus devices, and he just now posted SuperSU v2.23 BETA. This can be flashed via TWRP. This means you can now root any device running Kit Kat or Lollipop if you have custom recovery installed on your device. This is also a bit simpler than booting into fastboot and running the commands to gain root. Chainfire stated in his release notes that several root apps that weren't working in Lollipop before may now be working. This is very much BETA and is untested so there could be ill side effects. If you would like to test this version of SuperSU head to the link below for the download.
via +Chainfire