Did a search for "brake rotor replacement" and, to my surprise, came up with nothing.

Question: On a 2006 V50 with 30,000 miles, should I expect to replace the front rotors when I do the brake pads? Obviously I can measure them and see what I've got when I pull the wheels off, but I wanted to know in general if I should order a set of rotors when I order the pads.

Usually you will be able to get atleast 2 sets of pads out of the rotors.
You should be fine for another set of pads.

If they are not rusted or pitted and you feel no pulsation while braking, just swap out the pads and clean and lube the slides and pad mounts.

Rotors are rotors are rotors. And like many things, the answer to your question is "it depends".

First, all rotors have minimum thickness specs. If your's measure less than
minimum thickness (as measured by caliper tool, not eyeball) then you'll need new rotors. Remember that pad wear does wear rotors (although not usually significantly) and machining the surfaces wears them more.

Second, a score in a rotor can cause need for replacement. If, for instance, you ignore pads and you get metal to metal contact, you can score the surface of your rotor. If the gouge is deep enough (see point 1 above) you can't machine it out and will need a new rotor. I want to thank Chrysler for personally reminding me of this point -- stuck caliper on wife's car = worn out pads = scored rear rotor = new rotor at one wheel.

Third, the other reason to replace a rotor is because it becomes warped from excessive heat or other abuse. You'll feel that as a pulse in the brake pedal. I learned this on a '73 Camaro the hard way, too. That one was my fault.

Rotors are not a normal service replacement item.

If, as in motorcycles, you can buy a variety of pads of differing friction
coefficients, you might need new rotors with a different surface/hardness.
But unless you race, this isn't likely.