You don't have to root your phone to use Cerberus. However if you want to keep Cerberus running even after a factory reset you have to do this (from Cerberus FAQ):

The easiest way to install Cerberus as a system app is with the "Convert to system app" feature of Link2SD: install the app, open it, long-press on Cerberus in the list of installed apps and select "Convert to system app".

I had Cerberus installed for several years. I converted it to be a system app after watching the video. Now I secretly hope to be able to record something similar if it gets stolen.