Heat a charcoal grill or set a gas grill to high; bank coals or turn off burner on one side. Brush steaks with half the oil and season with salt and pepper. Grill on hottest part of grill, flipping once, until browned, 4-6 minutes. Using rosemary sprigs as a brush, baste steaks with remaining oil. Cook to desired doneness, 4-6 minutes more for medium rare, or until an instant-read thermometer reads 125°. If the outside starts to burn before the steak is fully cooked, move to the cooler side of the grill until done. Let steaks rest 5 minutes; slice against the grain along the bone. Serve with lemon wedges.