Preheat the oven to 450 degrees F and arrange a rack in the lower third.
Combine 1 tablespoon of the oil, garlic, 1 tablespoon salt, rosemary, and 2 teaspoons pepper in a bowl and mix to combine. Rub the mixture all over the roast and set aside at room temperature for 1 hour. (Can be done up to 12 hours ahead. Store covered in the refrigerator and bring to room temperature while oven heats).
Overlap the prosciutto on the meaty side of the roast and secure in place with kitchen string, tie the roast by running the string parallel to the bones. Arrange the roast in a large roasting rack, bone side down. Roast until the meat is nicely browned, about 25 minutes.
Put the figs and shallots in a bowl and add the remaining 1 tablespoon oil, vinegar and honey. Season well with salt and pepper, to taste, and toss to coat. Add the fig mixture to the roasting pan, reduce the oven temperature to 350 degrees F, and roast for another 1 hour and 10 minutes. Baste the vegetables occasionally, until the internal temperature registers 115 to 120 degrees F on an instant-read thermometer. (Be sure the thermometer is exactly in the center of the roast.)
Remove the roast from the oven and transfer it to a cutting board. Cover it tightly with aluminum foil and allow the meat to rest for 20 to 30 minutes. Remove kitchen string, carve, and transfer to a serving platter. Serve with the figs and onions.