Gather the ingredients.

Combine the oil, salt, dried thyme, onion powder, dried oregano, apple cider vinegar, pepper, dried tarragon, mustard powder, chili powder, and garlic in a small bowl.

Place prime rib roast on a large cutting board. Spread seasoning evenly over the roast, making sure it is well coated. Let sit at room temperature for 1 to 2 hours before cooking. Prepare grill for rotisserie cooking following the instructions in your grill manual. You may have to remove the grill grates.

Run the rotisserie skewer through the center of the roast and loosely secure with the rotisserie forks.

Place roast into the rotisserie mechanism on grill, adjusting to ensure the roast is centered. Tighten the forks.

Place an aluminum drip pan below the roast and turn the rotisserie on briefly to make sure there is enough room for the roast to turn freely without hitting the pan. If not, adjust the skewer.

Remove roast and drip pan from grill. Preheat grill to a high (500 F to 600 F) temperature.

Using heat-resistant gloves, return the roast to grill once the grill is hot. Place the drip pan under the roast.

Add 1 cup of water to the drip pan to lend moisture to the meat as it cooks.

Cover the grill. With the rotisserie on, grill the meat on high for 20 minutes, then reduce the temperature to medium-low (300 F). You may have to shut the middle burner, and/or adjust the outer burners to maintain this temperature. Continue cooking with the cover closed until the internal temperature of the meat reaches at least 120 F (140 F for medium), about 1 ½ hours (start temping the meat early, after about 1 hour at the 300 F temperature).

Using heat resistant gloves, remove meat from the grill and the rotisserie rod, cover with aluminum foil, and let rest for 15 to 20 minutes.

Stand the roast on a cutting board so the bones are pointing up.

Carve along the bones to remove the meat in one piece.

Set the meat on its cut side and cut across the grain into ½ to ¾-inch thick slices. Place onto a platter and serve.