If any silver skin on loins is present, cut away and discard.
Sprinkle sage, garlic, salt and pepper all over loins. Place loins closely together lengthwise, with thick ends meeting thin ends, to even out roast thickness.
Lay out slices of bacon snugly together on a cutting board, forming a rectangle. Place loins across bacon so bacon ends emerge from each side. Beginning at one end, lift a bacon end up over loins at a 45° angle. Then, alternating sides, continue lifting bacon ends down the length of roast forming a chevron pattern of bacon on top.
Cut five 12-inch (30-cm) lengths of twine and one 30-inch (75-cm) length. Place 5 shorter lengths of twine under loins widthwise. Working out from roast centre, firmly (but not causing deep indents to form) tie up each piece of twine, spacing evenly apart. Then tie up roast lengthwise with longer piece of twine. Trim twine ends; discard. (Roast can be prepared, covered and refrigerated for up to half a day. Add 10 to 15 minutes to roasting time.).
When ready to roast, preheat oven to 425°F (220°C).
Heat a large frying pan over medium heat. Lightly brown roast on all sides, about 15 minutes in total.
Transfer to a baking pan lined with a rack. Place in oven; set time for 30 minutes. Check and continue roasting until a meat thermometer reads 145°F (63°C).
Remove from oven: transfer to cutting board. Cover roast with foil; let rest 15 to 20 minutes.
Meanwhile, peel core and slice apples. Thinly slice onion.
Drain most of fat from frying pan; place back over medium heat. Add onion; cook 10 minutes or until lightly browned. Stir in flour; cook 1 minute. Stir in chicken broth; add apple slices.
Bring to a boil; simmer, covered, 5 to 10 minutes or until apples are tender and sauce is lightly thickened. Add more broth if too thick; keep covered and hot.
To slice pork roast, snip off lengthwise string. Then slice about ¾ inch (2 cm) thick, removing crosswise strings as they are encountered.
Place a few saucy apples on each warm serving plate, top with a couple of slices of roast and drizzle with more sauce. Serve with mashed potatoes and a steamed julienne of carrots.