You need to be rooted to install a custom recovery, or to install a ROM with the loki patch.
Not to mention, if you're rooted you can download ROM manager, and have it put the custom recovery on for you.
I didn't have to root my HTC One to install a custom recovery. I just unlocked my bootloader and installed TWRP. I then flashed a ROM that was already rooted.
Either way, it doesn't matter. The two processes basically go hand in hand.