Preheat oven to 325°F. Trim fat from meat. Stir together mustard, maple syrup, sage, orange peel, ¼ teaspoon salt, and the pepper. Spoon mixture onto the meat. Line a roasting pan with foil, if desired. Place the roast, fat-side up, on a rack in the shallow roasting pan. Insert a meat thermometer into center of the roast. Roast, uncovered, for 45 minutes.
Meanwhile, peel a strip of skin from the center of each potato. Cook the potatoes in a covered large saucepan in enough boiling salted water to cover for 5 minutes. Add carrots; cook for 5 minutes more. Drain.
Toss together the potatoes, the carrots, the olive oil, and the remaining ¼ teaspoon salt. Place in the roasting pan around the pork roast. Roast, uncovered, for 45 minutes to 1 hour more or until the meat thermometer registers 155°F. Remove the roast from the oven; cover with foil. Let stand for 15 minutes before carving. (The meat's temperature will rise 5°F during standing.)