It depends on the rules. Jon Jones could just not let Roger take him down and stall around in the standup grappling after scoring like 1 point. He could definitely make Roger look like a joke doing that. BJJ guys takedowns are piss poor, wreslters' takedown defenses are top notch, and even C-level wrestlers can exploit that to dominate the best BJJ guys on the planet.
It's 2 different levels of competition. It's like kickboxing vs boxing. Kickboxing might be a superior martial art. However, boxers will always win because the top-level A-level athletes are simply on another planet than the part-time construction workers that dominate BJJ.
Wrestling is an international sport practiced everywhere. BJJ is... what? A fringe sport that wasn't even fringe until 1993?