Step 1: Remove the rib roast from the refrigerator at least 3-4 hours before cooking. This allows it to come to room temperature, ensuring a more even cook. Pat the roast completely dry with paper towels.
Step 2: In a small bowl, combine coarse salt, black pepper, garlic powder, onion powder, dried rosemary, and dried thyme. Rub the mixture generously all over the rib roast, pressing it into the meat. If desired, you can lightly coat the roast with olive oil before applying the rub for better adhesion.
Step 3: Preheat your oven to 250°F (120°C). Place the chopped onions, carrots, celery, fresh rosemary, and fresh thyme in the bottom of a large roasting pan.
Step 4: Place the seasoned rib roast on a V-rack or roasting rack set inside the roasting pan, ensuring it's elevated above the vegetables. If bone-in, the bones can serve as a natural rack. Insert an oven-safe meat thermometer into the thickest part of the roast, avoiding the bone.
Step 5: Roast in the preheated oven until the internal temperature reaches 120-125°F (49-52°C) for medium-rare, or 130-135°F (54-57°C) for medium. This slow roasting process will take approximately 2.5 to 4 hours, depending on the size of your roast.
Step 6: Once the desired internal temperature is reached, remove the roast from the oven and transfer it to a cutting board. Tent loosely with aluminum foil and let it rest for at least 30-45 minutes. Do not skip this step, as it allows juices to redistribute.
Step 7: While the roast is resting, increase your oven temperature to 450-500°F (230-260°C).
Step 8: After resting, return the roast to the very hot oven (without the foil) for 10-15 minutes, or until a beautiful, deep brown, crispy crust has formed. Keep a close eye on it to prevent burning.
Step 9: Remove the rib roast from the oven for a final rest. Let it sit uncovered for another 15-20 minutes before carving.
Step 10: To carve, carefully cut away the chined bones if they are still attached. Then, slice the meat against the grain into desired thickness. Serve immediately with the pan drippings or a homemade au jus, and your favorite holiday side dishes.