Combine first 6 ingredients in a large shallow dish or large zip-top plastic bag. Pierce pork several times with a fork, and add to marinade. Cover dish or seal bag; marinate in refrigerator at least 2 hours.
. Preheat oven to 350°.
. Remove pork from marinade, reserving marinade. Place pork in a shallow roasting pan; add apple, pear, and onion. Pour reserved marinade over pork, apple, pear, and onion; sprinkle evenly with brown sugar. Bake at 350° for 1 hour or until thermometer registers 155° (slightly pink). Place pork on a serving platter, and let stand 10 minutes.
. While pork stands, place flour in a medium saucepan. Carefully pour pan drippings into pan, stirring with a whisk until well blended. Stir in syrup. Bring to a boil; reduce heat, and simmer 1 minute or until gravy begins to thicken.
. Slice roast; serve with fruit, onion, and gravy. Garnish with rosemary sprigs, if desired.