
With a sharp knife, cut the bones off of the roast by running the knife down the bones between the rib rack and the thick roast. This will keep the ribs all in one piece when separating them from the roast. Remove the ribs from the roast and set the ribs aside.
Cover the roast loosely with plastic wrap and let it stand at room temperature for 3 hours.
In a small bowl, mix together the oil, rosemary, thyme, salt, pepper, and garlic. Pat the roast dry with paper towels and rub the herby oil mixture all over the meat.
Replace the ribs back on the bottom side of the roast. Use butcher’s twine to tie them tightly in place, in 1-inch intervals.
After 2½ hours of resting, preheat the oven to 500°F.
Place the roast rib-side down in a large cast-iron skillet or roasting pan. Cook at 500°F for 15 minutes. Reduce the oven temperature to 325°F and continue cooking for 2 hours to 2 hours and 10 minutes, until an instant-read thermometer measures 125°F for medium-rare. The roast will continue to rise in temperature 5 to 10°F while it rests.
Carefully move the roast to a cutting board and tent it with foil. Let it rest for 20 to 30 minutes.
Cut and remove the butcher’s twine and ribs. Slice the roast to your desired thickness and serve.