In a small bowl, mix together all of the rub ingredients. Using your hands, coat the meat in the olive oil and then smear the rub all over. Transfer the meat to a plate, cover with plastic wrap and chill in the fridge for at least 1 hour, or up to 4 hours.
Preheat a grill to 225°F. Remove the roast from the fridge 30 minutes before you are ready to cook it so it can come up to room temperature.
Place the meat on the preheated grill and slow cook until it reaches an internal temperature of 125°F for medium rare, approximately 3 hours. Remove the meat from the grill, cover with foil and let rest for 10 minutes before serving.
Bison meat does not marble like cow’s meat so it is a lot leaner. Bison meat can take a third less time to cook compared to beef and is best eaten rare to medium rare. Cooking times can vary depending on the thickness of the meat so I strongly recommend using a meat thermometer to help you know when the meat is cooked.