Sauté onion in a skillet coated with cooking spray over medium-high heat 3 minutes or until tender. Add bread cubes, 2 tablespoons wine, milk, and next 5 ingredients, and stir well. Spoon 1 heaping tablespoon bread mixture onto each piece of veal. Roll up jelly-roll fashion, beginning at narrow end, and secure with wooden picks. Place the flour in a shallow bowl. Dredge the veal rolls in flour, turning to coat; shake off the excess flour.
Melt margarine in a large nonstick skillet coated with cooking spray over medium heat. Add veal rolls, and cook for 3 minutes or until lightly browned, turning frequently. Remove from skillet, and set aside. Wipe drippings from skillet with a paper towel.
Add the lemon juice, broth, and remaining 1/4 cup wine to skillet; bring to a boil. Return veal rolls to skillet; top with mushrooms. Cover, reduce heat, and simmer 10 minutes or until veal is tender. Remove veal rolls from skillet; discard wooden picks. Cover and keep warm.
Add the quartered artichoke hearts to the skillet. Combine cornstarch and water; stir well, and add to the skillet. Bring to a boil; cook 1 minute or until sauce is thickened and bubbly, stirring constantly. Pour sauce over the veal rolls, and garnish with lemon slices, if desired.