Position a rack in the middle of the oven and preheat to 500 degrees . Arrange the tomatoes cut side up on a parchment-paper-lined baking sheet, drizzle 2 tablespoons olive oil on top and season with salt and pepper; roast until tender, about 20 minutes. Transfer the tomatoes and any juices to a large bowl.
Meanwhile, during the last 5 minutes of roasting, brush 1 tablespoon olive oil onto the cut sides of the hoagie rolls, season with salt and toast in the oven. Rub each toast with the garlic clove.
Bring a large pot of salted water to a boil. Add the tortellini and cook according to package directions, adding the green beans for the last 2 minutes of cooking; drain. Add to the tomatoes along with the mozzarella, parsley and remaining 2 tablespoons olive oil; toss and season with salt and pepper. Serve with the garlic toasts.