Ok, here's how I do my "prime" rib.
Start with a standing rib roast. I prefer bone in if you can get it. In this case, 3 bones, 7 pounds, Harris Ranch USDA Choice. Prime is best, but choice works fine in this application. Have your butcher trim some, but not all of the fat and partially remove the roast from the bone.
Roast a lot of garlic. I usually use fresh heads, but I was super pressed for time today. For a roast this size, you will need 6 or 7 heads. Once roasted the garlic becomes very mellow. Roasted garlic recipe: cut heads in half through the equator, drizzle olive oil over the top, seal tightly in heavy duty foil, roast at 350 for about an hour.
Let cool and use a fork to mash into a paste.
Liberally apply this paste all over the roast. Make sure to season the part between the meat and the bone. In this case, I didn't apply the paste to the sides because I have friends who prefer their meat more done so they usually select the end pieces.
Get your seasoning ready. I just use Hawaiian salt, fresh cracked pepper and fresh thyme.
Now generously season the roast. This may look like a ton of salt, remember that when you slice it, the crust will only be on the edges. I lightly seasoned the sides.
Preheat your oven to 225. I should have mentioned that you should take your roast out of the fridge for about an hour or two so that it comes to room temperature. Place it in a pan and use a thermometer to acquire the perfect temperature. Since this roast is bone in, technically you don't need a rack, but whatever.
This thermometer lists rare as 135 which is conservative. In my opinion, this is getting to medium rare. Also the temperature will rise about 3-5 degrees in the 20-30 minutes while resting. I estimate that this size will take about 4 hours at this temperature. When I get to within 7 degrees of my desired internal temperature, I turn the oven up to 400. This will form a nice golden crust. You should watch your roast during this process so it doesn't burn. The roasted garlic will become bitter if you burn it.
Looking good.
Used the bones to make au jus.
Medium Rareish
Served up with haritcot verts & creminis and fingerling lyonnaise.