11 lb boneless Prime Rib Roast

Lots of ways to do these. I usually like to do this crust

1 tablespoon allspice berries
3 tablespoons black peppercorns
3 tablespoons yellow mustard seeds
3 tablespoons coriander seeds
2 tablespoons cumin seeds
3 tablespoons kosher salt, plus more for seasoning
One 6-rib standing beef rib roast (14 to 15 pounds), 1/2-inch fat cap left on the meat

You could roast at 375 or do a reverse sear, but like I warned on another thread today it can get firey and difficult the larger the cut. I would put it on a rack or something to easily pick it up. I like doing 275 until 120 then opening vents to get up closer to 500 to do the sear to desired temp without having to open the egg and burn my arm hair off or risk dropping it.

I also love a good horseradish cream sauce

2 cups plain Greek yogurt
1/4 cup plus 2 tablespoons drained grated horseradish
2 tablespoons grated fresh ginger
1 tablespoon freshly ground black pepper
1 teaspoon sugar

Time to cook depends on thickness, not weight. For round items weight works pretty good as an estimate. With beef rib roasts, once you get to a three rib roast the thickness doesn't get any greater with the increased weights of larger roasts. At 250° you are looking around 2-3 hours.

Low temp indirect first.  Finish at high temp. Your choice of direct or indirect for the high temp finish. Some prefer to go direct over high heat - gets a nice crust quickly, but can be a pain to handle a big piece of meat over the hot coals. Others prefer to stay indirect but go to around 550º or so - Less handling of hot platesetter,etc. but tends to take longer to get a nice crust which might lead to cooking the interior a bit more than desired.  Both work well, so use what you feel more comfortable with.