Your butcher can remove the bones and trim excess fat from the roast; just make sure that the bones are packed up along with the meat, as you need them to protect it from overbrowning. If the only roast you can find is boneless, fashion a protective "bone" from aluminum foil (see instructions below). Letting the roast stand at room temperature for 2 hours prior to grilling helps it cook evenly. Serve the roast as is or with Horseradish Sauce.
1. Rub roast with oil and season generously with pepper. Spread salt on rimmed baking sheet; press roast into salt to coat evenly on all sides. Tie meat back onto bones exactly from where it was cut, passing two lengths of twine between each set of bones and knotting securely. Refrigerate roast, uncovered, for 1 hour, then let stand at room temperature 2 additional hours.
2. Meanwhile, soak wood chunks in water for 1 hour; drain. About 20 minutes before grilling, open top and bottom grill vents. Using chimney starter, ignite 4 quarts charcoal briquettes (about 60 coals) and burn until partially covered in thin, gray ash, about 15 minutes. Empty coals into grill; build modified two-level fire by arranging coals to cover one-half of grill. Place disposable roasting pan on empty side of grill. Position cooking grate over coals, cover grill, and heat until hot, about 5 minutes; scrape grate clean with grill brush.
3. Place roast on grate over hot side of grill and sear on fat-covered sides until well browned, turning as needed, 8 to 10 minutes total. (If flare-ups occur, move roast to cooler side of grill until flames die down.) When thoroughly browned, transfer roast to cooler side of grill, bone side down, with tips of bones pointed away from fire. Place soaked wood chunks on coals. Cover grill, positioning top vent over roast to draw smoke through grill. Grill-roast (do not remove lid for at least 1 1/2 hours) until instant-read thermometer inserted into center of roast reads 125 degrees for medium-rare, 2 to 2 1/2 hours.
4. Transfer roast to cutting board and let rest 20 minutes, lightly tented with foil. Remove strings and bones, cut into 1/2-inch-thick slices, and serve.