Alignment doesn't usually affect cupping. Mis-alignment causes abnormal wear, but not cupping.
Cupping is usually caused by too-hard of a tire that "bounces" somewhat down the road caused by either too high psi or worn shocks, but cupping is just as commonly caused by lack of rotation. It is normal for your tires to cup if you've neglected to regularly rotate them or if you ride them very hard.
Some tires naturally cup more than others, and some vehicle/tire combos can lead to unimaginable extreme cupping when the same tires work fine on another vehicle.
When you say "cross-rotated" what specific pattern did they do?
Normally on a RWD vehicle, the back wheels go straight to the front and the front wheels criss-cross to the rear. That is for "uncupped" tires.
However, in my experience (and what worked to correct my ATs) the quickest way to correct the cupping is to swap them in an X-pattern so that each tire not only changes from front to back but also changes rotation.
This, combined with running 42psi in all 4 tires, corrected mine in under 1000 miles.
Also...don't be alarmed if the truck rides WAY worse when you first rotate the cupped tires. This won't last long, and the excessive cupped noise will go away...quickly. When I first rotated my badly cupped AT rears to the front it sounded like a jet plane going off for about 100 miles. The tires wore down flat in a matter of a few hundred miles until they were completely flat...and they were cupped as bad as yours.
Give it a chance to work, and keep the psi lower. They'll be fine. Make sure they rotated them properly.
