Preheat grill for medium-high heat. We will be cooking this roast indirectly, so set up your grill accordingly.
Combine the salt, black pepper, onion powder, and granulated garlic in a small bowl. Set aside
You’ll need to create a pilot hole through the center (lengthwise) of the roast. This will help guide the rotisserie rod through. Once you've made the pilot hole and have run the rod through the roast, secure the forks.
Place the rod onto the rotisserie until on the grill and set the aluminum pan underneath. Fill the pan with hot water, close the lid, and cook the roast for 1 1/2 hours. Check ever so often to make sure the drip pan does go dry. This liquid makes a great jus or gravy once the roast is done.
I recommend cooking until the meat reaches an internal temperature of 140 degrees F., between medium and medium-rare. Watch for shrinkage as the meat cooks, and adjust the forks if needed.
Once the roast is cooked, remove from heat with rod and forks still intact. Heat resistant gloves work really well for this job. Place onto a clean wooden cutting board, loosely tent with aluminum foil, and let the meat rest for 20 minutes.
Carefully loosen forks and remove the rod. Cut into thin slices and use however you wish. Serve topped with gravy and mashed potatoes, or use in sandwiches, salads, and wraps.