Does rooting (but no custom roms) trigger knox's void warranty Does it make Knox's "void warranty" = 0x1
There are two events that will trigger the Knox flag to change from 0x0 to 0x1.


Unsigned recovery (recovery.img) is flashed
Unsigned kernel (boot.img) is flashed


It's not the actual custom rom that trips Knox when you get to flashing. It's the step before that, getting a custom recovery loaded in order to flash the rom itself.

This is also why the de-la-vega root method works, because it flashes a prerooted stock system image to your device without touching the two partitions that DO trip Knox of modified.