HEAT oven to 325°F.
COOK vegetables in margarine in large skillet on medium-high heat 3 to 5 min. or until crisp-tender. Remove from heat. Stir in 2 Tbsp. mustard, then bread, apples and seasoning.
OPEN roast, cut-side up, on work surface. Spread with 2 Tbsp. of the remaining mustard; top with bread mixture. Re-roll roast; tie closed with kitchen string. Place on rack in roasting pan.
BAKE 2 hours or until done (145°F). Transfer roast to carving board; let stand 10 min.
MEANWHILE, spoon 1 Tbsp. meat drippings into small saucepan; whisk in flour. Cook on medium heat 1 min., stirring constantly. Add apple juice and remaining mustard; cook and stir 5 min. or until sauce thickens and starts to boil. Remove from heat; stir in parsley.
SLICE roast; discard string. Serve meat topped with mustard sauce.