*If you want to serve this roast around 5:30pm, you'll need to start this process at 11am.Remove roast from fridge 1 hour before starting to cook to let it come up to room temperature. Preheat oven to 250 degrees F about 30 minutes into the hour. Once the oven is preheated, leave it at 250F for 30 minutes.
While the oven stays hot, remove standing rib roast from packing and place on a cutting board or baking sheet. Drizzle oil over roast and use your hands to spread it all over. (You may not need the entire 2 tablespoons, just enough to make sure all the surfaces have a light coating.)
In a small bowl, stir together the salt, pepper, and garlic powder. Rub all of the seasoning mix over every surface of the roast.
Transfer the roast to a roasting pan (without a rack). Place roast bone side down; the bones will act as the rack.
Insert the probe for your meat thermometer into the top center of the roast. Push the probe into the meat until it's about halfway in. You don't want it touching the bones.
Turn oven down to 200 degrees F. Place roast on middle oven rack, close oven, and connect probe to meat thermometer. Set thermometer alarm for 118 degrees F. Cook the roast until the alarm goes off, about 3.5 to 4 hours for this size standing rib roast.
Remove roast from oven. Cover with foil. DO NOT remove probe. Make a tear in the foil to allow it to go around the probe. Rest the roast while you heat the oven to 500 degrees F.*Your roast may go up in temperature while it's resting. That's okay. You want it to finish around 125F to 130F for medium-rare.
Once oven is at 500F, remove foil (save foil) and place roast back in the oven. Cook for 10 to 15 minutes, or until a nice crispy crust forms and the fat cap breaks.
Remove from oven and transfer to a cutting board. Recover with the same foil (leave probe in) and let rest for at least 20 minutes. Don't skip this resting period! It's important to let the meat rest. *If your roast finished sooner than expected, you can leave it resting like this until you're ready to serve.
Once rested, remove foil and probe. Flip the roast over and use a chef's knife to cut the bones from the meat. Try to stay as close to the bone as you can, and take them off as one rack. (Don't cut in between in bones.) OR if your butcher tied the bones on for you, remove the ties and bones.
Flip the roast back over. Cut off the end piece (this will be almost well done). Cut the prime rib into 8 slices (about 1-inch thick). You can cut slices thicker or thinner per your diner's request. Serve immediately with jus and horseradish sauce, if desired.
Red Wine Jus
Pour off the fat from the roasting pan, but save all those brown bit in the pan. Place the roasting pan on the stove over medium heat.
Pour in beef broth to deglaze the pan. Use a wooden spatula (or spoon) to scrape the brown bits off the pan. Pour in the red wine and bring to a simmer.
Once the jus has reduced by half, remove from heat and stir in butter until melted. Strain through a sieve and pour into small bowls for serving.
Creamy Horseradish Sauce
Stir together horseradish, sour cream, and mayo in a bowl until combined. Serve immediately.*You can easily double or triple the sauce ingredients if you're serving a large group.
If you're not comfortable cutting the bones from your roast, have your butcher remove the bones and then tie them back on for you. Otherwise, you can leave the bones attached and remove after roasting - just be sure to have your butcher remove some of the excess fat along the bone line.
The size of your roast will vary. I asked for a 4 bone roast and it came out to around 11 pounds. We're basing our cooking time on temp, not weight so get whatever size roast works for you.
Plan on feeding 2 people per rib. This 4 bone roast will serve about 8 people.
Nutrition is for the roast only. The jus and hoseradish sauce are not included.