Let the roast sit at room temperature for 1 hour before roasting.
Position a rack in the lower third of the oven and preheat to 500 degrees . Generously season the roast with salt and pepper; place on a rack in a roasting pan. Insert an ovenproof meat thermometer in the center of the roast.
Slice off the top half-inch of each garlic bulb to expose the cloves. place the garlic on a large sheet of foil, drizzle with the EVOO and season. Wrap in the foil.
Transfer the roast and garlic to the oven. Cook for 10 minutes. Lower the oven temperature to 350 degrees ; after 1 hour, remove the garlic and let cool. Continue cooking the roast until the thermometer registers 125 degrees for medium-rare, about 1 1/2 hours longer.
Transfer the roast to a large cutting board, tent with foil and let rest for 20 minutes. (Reserve the pan with the drippings.)
Unwrap the garlic. Squeeze the roasted garlic into a cup.
Place the roasting pan over medium heat. Add the wine and bring to a simmer. Cook, stirring occasionally, until the liquid is reduced by half, 7 to 8 minutes. Transfer the juices to a medium saucepan; whisk in the broth, roasted garlic and mustard. Simmer the gravy until thickened slightly, 5 minutes. Whisk in the lemon juice; season.
Carve the roast at the table; serve with the gravy and potatoes.