Pork Roast with Sweet Potatoes, Pears, and Rosemary

3 1/2 lb. bone in pork center loin roast, excess fat trimmed
1 Tbsp. olive oil
1 Tbsp. fresh rosemary, chopped, plus more for garnish
salt and freshly ground black pepper
2 1/2 lb (about 6 medium) sweet potatoes, peeled, and cut lengthwise into sixths
3 firm-ripe Bosc pears, quartered lengthwise and cored
12 oz. bottle hard cider (can substitute 1 C. apple juice & 1/2 C. dry vermouth OR use all apple juice)

Preheat oven to 450 degrees. Rub pork with oil. Mix rosemary, 3/4 tsp. salt, and 1/2 tsp. pepper in a small bowl. Rub over pork. Place pork, bone side down, in a large roasting pan. Roast 15 min. Reduce oven temperature to 350 degrees. Roast 15 min. Add sweet potatoes and pears to the pan, stirring to coat with pan juices, and spread around the roast. Salt and pepper to taste. Roast, occasionally stirring sweet potato mixture, until meat thermometer reads 145 degrees at thickest portion and potatoes and pears are tender, about 1 hr. Transfer pork to carving board and sweet potato mixture to ovenproof bowl, tent the bowl with foil and keep warm in turned-off oven.
Let pork stand 10-15 min.
Heat roasting pan over high heat. Add cider, bring to a boil, scraping up pan drippings with a spoon. Boil until reduced to 3/4 C., or about 5 min. Pour into sauceboat. Carve pork. Transfer to serving platter, surround with sweet potato mixture, drizzle with 3 Tbsp. cider sauce and sprinkle with rosemary. Serve with remaining sauce on the side.