Add the rosemary, pepper, salt, paprika, cayenne, garlic powder, and celery salt to a small mixing bowl and mix well. Place in a shaker and set aside.
Rack of Lamb
Remove the skin from the lamb rack, leaving a good layer of fat still on the meat.
Apply the rub evenly from the shaker and place the lamb uncovered in the fridge for a few hours or overnight.
Prepare to cook using offset/indirect heat. Preheat your pit to 250 degrees F (96 degrees C).
Place the lamb rack directly on the grill in the pit for about 45 minutes. Check for the desired doneness, 130 degrees F (54 degrees C) for medium-rare or 140 degrees F (60 degrees C) for medium.
Remove from the grill, wrap tightly in foil, and allow to rest for 10 minutes. Slice and serve.