Season: In a small bowl, combine the olive oil, salt, pepper, garlic, allspice and fresh herbs. Score the fat cap with a knife, creating a diamond pattern. Rub the seasoning on all sides. Let rest at room temperature for 1 hour.
Heat Grill: Add a cup of wood pellets to the Ninja Woodfire Grill smoke box. Set the grill function to smoker. Set the temperature to 250F degrees and the time to 3 hours.
Smoke: Add the prime rib to the smoker with the fat cap up. Smoke for about 90 minutes, or until the internal temperature reaches 105F degrees.
Sear: Increase the grill temperature to 400F degrees. Cook the roast for 15 more minutes, or until the internal temperature reaches 125F degrees.
Rest: Remove the roast from the grill. Tent loosely with foil and let rest for 15-30 minutes before slicing and serving.
Video
Notes
If you prefer your roast cooked further than medium rare, let it sear an additional 5-15 minutes. If you like it really well done, so there is no pink, keep an eye on the crust during this phase, so it doesn't burn.