Prepare your smoker according to the manufacturer’s instructions. Preheat it to 225°F (107°C) and add your wood chips for smoking.
In a large dish, combine kosher salt, black pepper, garlic powder, onion powder, smoked paprika, and cayenne pepper (if using). Mix well to create a dry rub.
Pat the prime rib roast dry with paper towels for better seasoning penetration.
Rub the olive oil all over the roast, then generously apply the dry rub, making sure to coat all sides of the meat. Allow the roast to sit at room temperature for about 30 minutes to absorb the flavors.
Once the smoker is ready, place the seasoned prime rib roast onto the grill grates fat side up. Insert the meat thermometer into the thickest part of the meat, avoiding the bone.
Smoke the roast for approximately 4 hours, or until the internal temperature reaches 130°F (54°C) for medium-rare. Remember that the temperature will rise a few degrees while resting.
Once the desired temperature is reached, remove the roast from the smoker, and wrap it loosely in aluminum foil. Let it rest for 20-30 minutes to allow juices to redistribute.
After resting, slice the prime rib against the grain into thick slices. Serve with your favorite sides and enjoy!