In a large bowl, combine bread crumbs, garlic, rosemary, 1 teaspoon salt and 1/4 teaspoon pepper. Toss in 2 tablespoons olive oil to moisten mixture. Set aside. Season the rack all over with salt and pepper. Heat 2 tablespoons olive oil in a large heavy oven proof skillet over high heat. Sear rack of lamb for 1 to 2 minutes on all sides. Set aside for a few minutes. Brush rack of lamb with the mustard. Roll in the bread crumb mixture until evenly coated.
For oven cooking, place the lamb in an uncovered roasting pan and cook at 165 degrees C (325 degrees F). For every 0.5 cm (inch) of thickness, allow 10 to 15 minutes of cooking time. You can allow more time for a well-done steak, cooking to an internal temperature of 76 degrees C (170 degrees F).
Instead of roasting lamb chops in the oven throughout cooking, consider searing the meat on high-heat first. You can use a small amount of oil and a large skillet to sear the lamp chops for about three minutes on each side. The skin of the chops should be browned before removing from the heat. Cover the lamb chops in a roasting dish after browning, and cook in a 400 degree Fahrenheit oven for 10 to 15 minutes depending on how well-done you want the meat. If you want lamb chops medium-rare, the internal temperature on the meat thermometer should register 140 degrees Fahrenheit.