This flavorful roast needs only six ingredients!
Preheat the oven to 350°. Place the lamb on a wire rack set inside a large roasting pan. Season all over with salt and pepper. Turn the lamb, fat-side up, on the rack. In a medium bowl, whisk the stock, juice, and garlic; season. Pour over the lamb. Place rosemary sprigs in the bottom of the pan.
Roast the lamb, basting every 20 minutes, until an instant-read thermometer registers 135° to 140° when inserted into the thickest part (do not touch the bone), 1 hour and 45 minutes to 2 hours. Transfer to a cutting board. Let rest for 15 minutes.
Strain the pan juices into a glass measuring cup. (If needed, boil the juices in a skillet until reduced to 1 cup.) Slice the lamb. Serve with the pan juices. Garnish with rosemary sprigs and pomegranate seeds.