It is almost garunteed that rooting your phone voids the warranty boot loader unlocked or not. If you break your phone phone or total it, I recommend that you keep it and say it got lost.
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Only reason to say "it got lost" is if you are submitting an insurance claim to get it replaced, in which case this would be fraud.
If you screw your phone up and its not covered just buy a new one. If you can't afford to buy a new one.. don't risk it and don't root.
That being said, I realize this thread is old... but... to answer the OP's question.
Unlocking the bootloader voids the warranty on all but Developer Edition Moto X's. There are 3 states the Bootloader on the X can be in. Locked, Unlocked, and RELocked. We can only toggle between Unlocked and Relocked, we can not set it back to locked. This status is visible on the fastboot/bootloader screen.
Rooting the phone can be seen as altering it from the manufacturer's specifications. And altering from MFG's specs voids the warranty (according to the papers that came with my X).
Rooting using something like SlapMyMoto, etc. can be undone via flashing your phone with the SBF/ROM for your phone. 4.4.2 will also undo the changes made by MotoWpNoMo (which was initially thought to be permanent). BUT the carriers can still tell if you ever rooted depending their preloaded software (example: VZProtect on Verizon does report back to their systems if you are rooted).
One other thing to consider is the CARRIER's Terms of Service which may supersede the manufacturer's warranty, if you try and deal with the carrier for warranty issues.