Heat oven to 400° F. Combine all the ingredients except the basil in a roasting pan. Roast for 20 minutes, stirring occasionally, until the tomatoes are just bursting. Carefully transfer the tomatoes to a bowl and set aside. Place the roasting pan on the stove over medium heat (or transfer the liquid to a small saucepan) and reduce the liquid until slightly thickened, about 5 minutes. Toss the tomatoes with the basil. Drizzle some of the thickened balsamic sauce on each serving.