How can I backup my rom.

I finally got my phone rooted on lollipop. I want to install the xposed framework but all the instructions say backup your rom. I rooted using Deodexed_ROM but when I do home button, volume, power. I don't see an option to backup my rom. I'm also confused does titanium backup only backup apps or can in do a full system rom backup that I can restore from in case of a looping boot when flashing.

thanks