For Spice Rub: Toast cumin seeds, coriander seeds, allspice and peppercorns in heavy skillet over high heat 2 minutes, shaking pan frequently. Add mustard seeds and celery seeds; toast 1 minute. Transfer to bowl; cool.
Grind toasted spices to a powder; stir in red pepper. Reserve 1 tsp spice rub for Barbecue Sauce.
For Veal: Season veal with 2 teaspons of salt. Press remaining spice rub evenly onto veal. Wrap in 2 layers of plastic wrap. Refrigerate 4 hours or overnight.
For Barbecue Sauce: Heat oil in medium saucepan over medium-high heat until hot. Add onion and garlic; cook and stir until onion is tender and browned. Place onion mixture, molasses, vinegar, tomato paste, 1 teaspon salt, spice rub and pepper sauce in food processor or blender container. Cover; process until smooth. Reserve 3/4 cup barbecue sauce for basting.
Return remaining barbecue sauce to saucepan. Cook over medium-low heat 15 minutes or until slightly thickened, stirring occasionally. Cover and refrigerate. Reheat and keep warm when ready to use.
Roast veal shoulder in 325°F oven 2-1/2 to 3 hours or until medium doneness, basting occasionally with reserved barbecue sauce. Carve into thin slices; cover and keep warm.
Serve 4 to 4-1/2 oz sliced veal with 1 to 1-1/2 oz barbecue sauce on sandwich roll.