Can pityriasis rosea on the belt line, constantly being pressed on from pants and belt, get irritated and display larger and darker than the rest of the rosea on the body. or would the pant and belt pressure have no effect on how its displayed?

Difficult to say: This is difficult to answer without an in-person exam, as it cannot be concluded for certain that the rash is even pityriasis rosea. Googling images of your rash can at times help but many waste literally hundreds of dollars trying to fix their skin because they thought they had one issue when it was actually another. I would hesitate to conclude anything legitimate based on your description.

suggest that you make sure that this rash is indeed PR. Should that be the case, once in a while, but not very often , pressure on a typical PR lesion cause come excessive irritation. Would see dermatologist to confirm dx and proper tx with top steroid creams.