Rinse chicken; pat dry with paper towels. Place each breast half between two pieces of plastic wrap. Working from the center to the edges, pound lightly with the flat side of a meat mallet into a rectangle about 1/8 inch thick. Remove plastic wrap.
Combine tomato, Parmesan cheese, the 1/2 teaspoon herb, and pepper in a small bowl. Spread tomato mixture over chicken rectangles. Fold in long sides of each chicken rectangle. Starting from the short side, roll up chicken breasts to enclose filling. Secure with wooden toothpicks.
Combine the egg white and water in a shallow dish. Combine cornflake crumbs and the 1 teaspoon herb in another shallow dish. Dip each chicken roll into the egg mixture. Roll in the crumb mixture to coat.
To bake, spray a 3-quart square baking dish with nonstick coating. Place chicken rolls seam side down in dish. Bake in a 400 degree oven for 20 to 25 minutes or until chicken is tender and no longer pink. Remove toothpicks. Slice chicken rolls, if desired, and serve with warm spaghetti sauce over hot cooled pasta. Makes 8 servings.