At regular intervals, make 12 (1-inch deep) incisions into the pork loin, and stuff 1 garlic clove into each incision. Lay the rosemary branches across the loin and tie it tightly with butcher's twine, securing rosemary inside the twine.
Preheat the oven to 400 degrees F.
In a Dutch oven, heat the oil until just smoking. Season the meat with salt and pepper, brown it on all sides in the oil, remove and set aside. To the Dutch oven, add the onions, carrots, and apple and cook until light golden brown, about 8 to 10 minutes. Add the wine, bring it to a boil, and return the loin to the pan. Place the Dutch oven in the oven and cook 45 minutes, until the meat is fork-tender. Remove from the oven, remove loin and return Dutch oven to stove top to cook for 10 to 15 minutes more, until sauce is reduced. Garnish with the parsley, untie the loin and carve into slices to serve.