1. Preheat oven to 450°. Trim excess fat from lamb. Open lamb with cut side up. Smear pesto over meat. Sprinkle bread crumbs over pesto. Roll up lamb and tie securely with kitchen string at 2-inch intervals. Place in open roasting pan.
2. Roast lamb at 450° 15 minutes. Reduce oven temperature to 350° and roast 1 1/2 hours, or until medium-rare. Remove to cutting board and cut into thin slices to serve.