Preheat oven to 425°.
Combine first 8 ingredients in a large bowl; stir with a whisk. Add eggplant, yellow squash, bell pepper, and zucchini; toss gently. Place vegetable mixture in a jelly-roll pan. Bake at 425° for 20 minutes or until vegetables are tender, stirring occasionally.
Combine roasted vegetables and cubed tomato, and toss gently. Arrange vegetable mixture on bottom half of loaf, and top with cheese slices and top half of loaf. Place loaf on a jelly-roll pan, and bake at 425° for 5 minutes or until cheese melts. Cut loaf crosswise into 6 pieces.