That's a pretty good question.

I just got done doing the brakes on the three cars in our corral, a Barracuda, a Mustang, and a Camry.

On the Camry, one of the tire guys had overtightened the lugs so much that one of the lug studs was destroyed, and both rotors were warped. It was easier , cheaper and faster to replace both rotors.

On the Ford, I had one rotor resurfaced (no warpage), and replaced one (deep grooves on the surface). I had a machinist check, and they were not warped, though this machinist claims that all rotors will warp slightly due to heat.

The Barracuda had two straight rotors, but a caliper seized, and both brake hoses also needed replacement. When the Barracuda's caliper seized, I was afraid the rotor had warped since the it was so hot I could have cooked a slab o' bacon on it. But, apparently, I got lucky and the rotor did not warp.

It seems that turning warped rotors will probably put them out of specifications. The FSM should be your guide (and the machinist's too). But you're not going to be able to find some of these old Mopar rotors easily and cheaply. That's why I think your question is a good question, and I'll be interested to see the replies to this thread.