Preheat your oven to 375 degrees. Place the rack of lamb in a cast iron skillet, foil lined baking sheet, or roasting pan. Lay the 3 rosemary sprigs under the roast & 3 on the roast, like you did when marinating (use the same ones). Season the rack of lamb with salt & pepper. Roast for 20-30 minutes, depending on how done your like your lamb. The internal temperature should reach 130-140 for medium rare.