Any defective parts I got from Rock were replaced at no shipping cost to me.
The drum can get smacked out of round in shipping. I alert them to that when it happens, and they have always bubble wrapped the replacement drum box and then put it in another "large" box.
And they have always shipped the new parts out before actually receiving the bad part. They ship the new part as soon as they get the return tracking number when I drop off the bad part at the shipper to return it.
Rotors, that's a different problem all together. They can and sometimes do come out of tolerance. Rock has always made good on those to. I put the rotors on the car and check the lateral run out and thickness deviation before I mount the calipers.
Parts quality is so suspect now regardless of the parts source, that I always go through the calipers, wheel cylinders, master and install new hoses before installing the pads, shoes, drum and rotors.
It's been a long time since I burned up a drum or rotor.