Plan on 20 minutes per pound (15 pounds took about 5 hours)
Cut fat cap off the roast and rub with salt. Replace fat cap, wrap and let it set refrigerated for a day or two.
Unwrap and remove fat cap, coat with pre-made Prime Rib Rub then replace the fat cap and tie the meat into a nice rounded cylinder for even cooking. Wrap and refrigerate for another day.
Setup egg for indirect cooking, place drip pan on plate-setter under grill and bring heat to 250 degrees.
Set marinaded roast on grill and cook to 115 degrees internal temp.
Once roast reaches 115 degrees, open top and bottom vents and bring egg to 500+ degrees.
Remove roast from egg at 125 degrees internal temp and immediately wrap in foil and rest in an insulated cooler for at least 30 minutes or until eating time. It should cook under its own temperature to 135 +/-5 degrees.
Cut against the grain parallel to the bone lines and serve.