Transfer frozen prime rib roast at the bottom rack of refrigerator and thaw for 2 days.
Make the rub. Combine kosher salt, crushed peppercorns, rosemary leaves, thyme powder and garlic.
Brush prime rib with olive oil then spread the rub all over roast. Pat slightly so rub sticks to meat.
Place in a container uncovered and return to fridge to marinate for ½ a day or overnight.
Before roasting, remove from fridge and have it sit in the kitchen counter for 1 to 2hours to come to room temperature to cook evenly.
Insert thermometer from the side to the center of meat not touching the bones.
Pre-heat oven at 450 degrees F. Place uncovered prime rib roast at middle rack and sear for 20 minutes.
Set temperature at 300 degrees F after 20 minutes. Cook until thermometer reads 5 to 8 degrees lower your desired doneness. Note: When removed from oven and resting, prime rib roast will continue cooking.
Don’t follow the time instead rely on the thermometer temperature. I only provided the time so you have an idea how long it might take to cook.
For rare ribeye roast, cook for 2 to 2 ½ hours with internal temperature of 120 degrees F.
For medium to medium-well ribeye roast, cook for 3 to 4 hours. Internal temperature should reach between 135 - 145 degrees F.
For well-done ribeye roast, after 4 hours cover it with heavy duty foil. Continue baking for another ½ to 1 hour, depending on how well-done you like it. Internal temperature should reach 160 degrees F.
Note: Oven temperature varies, so adjust cooking time accordingly.
d. Remove from oven, if ribeye roast is uncovered, cover and let it sit for 10 to 20 minutes to rest. Roast will continue cooking so check thermometer until it reaches your desired doneness.
e. Crusty rub will fall once you start carving. If bone is attached with kitchen twine, remove twine. Typical prime rib serving is ½ inch but you can slice thicker.
If bone-in and attach, hold bone with prime rib upright. Use a boning knife, start trimming (or slicing) close to the bones and follow the curve until bones are removed.
Note: When you buy prime rib, you can request butcher to trim and reattach bone onto the roast with kitchen twine or you can do it yourself.
For Servings: Slice on the widest area ½ inch or thicker.
Allow 1 pound per person when buying prime rib roast.