It was a little before 10:30 on Tuesday morning when three-time world champion calf roper Tuf Cooper, riding a horse named Rambo, barreled out onto the arena floor of the Denver Coliseum. The son of the legendary roper Roy “Super Looper” Cooper was competing in a “slack round”: Whenever there are more competitors than available time slots in public rodeo performances, the ropers and wrestlers earn points toward the prize money during rides scheduled for slack or “off” hours.