Preheat oven to 400 degrees. In a roasting pan, combine tomatoes, eggplant, zucchini, onions, garlic, and olive oil. Roast until eggplant is tender, stirring occassionally, about 30 minutes. Turn mixture into a bowl and add vinegar, salt, pepper, water, and bread. Refrigerate and let sit several hours or overnight. In a food processor or blender, blend mixture until smooth. Put it through a food mill or strainer and discard solids. Check seasoning, garnish with garlic croutons or roasted tomatoes and serve.