- Combine garlic powder, onion powder, sea salt and pepper in small bowl; rub all over roast.
- Split your firebox into two heat zones; preheat NEXGRILL Revelry (or Charcoal Grill with Smoker) to 500ºF, turning half of burners to high and keeping the other half turned off.
- Place roast, fat side up onto grill over indirect heat; cook for 1 ½ hours.
- Place rosemary sprigs on grill to toast, about 10 seconds. Transfer to platter.
- Turn grill burners off without opening lid. The roast will continue cooking on the grill for another 45 minutes, for a total cooking time of 2 ¼ hours, or until instant read thermometer inserted into thickest part of roast registers 145°F for medium-rare.
- Transfer to cutting board, loosely tent with foil and let rest for 20 minutes before carving.
TIP: While the roast is resting, grill side vegetables of your choice on medium-high heat until lightly charred and tender, such as sliced and lightly oiled sweet potatoes and halved, par-boiled and lightly oiled Brussels sprouts.