Since posting this question I went on a tour for a few months which involved flying with my bike twice. Both times it was packed in a cardboard bike box from a bike shop.
It may have been unclear in my original question, but my question was specifically about the disc rotors, not how to pack a bike in general. When searching elsewhere I found there was lots of info about general bike packing, e.g. remove the rear derailleur wrap it in padding, use a dummy axle for the fork, etc, but I didn't find a lot of info on disc brakes.
Anyway, to be safe I removed the rotors, interleaved them with sheets of clean paper towel to avoid contamination (so three sheets total), then sandwiched them between two squares of press-board, which I then wrapped with duct tape. This may indeed be overkill but I'm sure it can't hurt. To keep the torx screws safe, I put them back in the holes they go in and screwed them in a few rotations. When I put the brakes back on I did not use any special alignment tool or torque wrench, I just used the torx driver on my multi-tool and put them in by hand.