Preheat the oven to 425°F. On a large baking sheet, toss the broccoli with the olive oil, salt, pepper, Italian seasoning, and garlic powder. Arrange in a single layer and roast until crisp-tender and just beginning to brown in spots, about 15 minutes. Remove from the oven and sprinkle with the mozzarella. Return to the oven until the cheese melts, about 1 minute. Remove from the oven and scatter tomatoes around the broccoli. Drizzle with the balsamic and sprinkle with the basil.