1. Preheat oven to 425ºF and line a baking sheet with foil. Combine tomatoes, mushrooms, bell pepper and onions in a large bowl, and toss with oil and salt. Season with pepper. Spread vegetables on baking sheet and roast until soft, about 25 minutes, stirring every 5 minutes. Toss with garlic and basil and set aside to cool slightly.
2. Split rolls or baguette in half lengthwise, and hollow out centers to make room for filling. Arrange 1/4 warm vegetables on bottom half of bread; top with 2 slices cheese and remaining bread. Press sandwiches to compact filling. Let stand 5 minutes until cheese softens, and serve.