Tie the roast at 2-inch intervals with butcher's string. Put it in a large resealable plastic bag.
In a blender jar or small food processor, combine the garlic, red wine vinegar, parsley, and rosemary. Add a couple of tablespoons of the oil and pulse to chop the garlic and herbs. Add the remaining oil in a small stream until the mixture is well blended.
Pour the herb mixture over the roast, coating it on all sides. Allow the roast to marinate for two hours at room temperature. (Or, you can refrigerate for several hours. Let the roast come to room temperature before roasting.)
Remove the roast from the marinade. Discard marinade. Liberally season the roast on all sides with Traeger Prime Rib Rub.
Place the roast, fat-side up, in a V-shaped rack in the roasting pan. Pour the beef broth into the bottom of the pan.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 450F (High) and preheat, lid closed, for 10 to 15 minutes.
Arrange the pan with the prime rib on the grill grate and roast for 30 minutes. Reduce the temperature to 250F (or Medium) and continue to cook until the internal temperature of the roast is 130F (for medium-rare), 2 to 3 hours.
Transfer the roast to a cutting board and let rest, loosely covered with foil, for 20 minutes. Meanwhile, make a jus. pour the drippings into a small saucepan or microwaveable container and skim off any fat that rises to the top. Taste the jus for seasoning, adding salt and/or pepper as needed. Rewarm before serving.
Carve the roast into thick slices and serve with the jus.