Preheat oven to 325 degrees. Place tomatoes on a nonstick baking sheet and drizzle with olive oil, salt and pepper. Roast for 45-50 minutes.
Once tomatoes are finished, heat a large griddle or skillet over medium heat. Brush the outsides of each slice of bread with olive oil, then place mozzarella on one slide, followed by tomatoes, basil (feel free to shred it if you'd like), more tomatoes and more mozzarella. Cook until cheese is melted and each side is golden, about five minutes per side. Drizzle with balsamic. Serve immediately.