They often aren't as flexible in the back and have difficulty using their hind end. Depends on the horse and amount of roach. Just for a solid riding horse - no competition then it may not have any bearing. A good saddle that is properly fitted and you would be fine. Mine has a very severe roach. She is a draft and we do use her for light work. No riding though. Not that it couldn't be done but she'd need a treeless saddle that is custom fit.