Place the tomatoes cut-side up in a shallow baking dish.
Drizzle with olive oil and sprinkle with salt, pepper and the thyme. Roast 1 hour 30 minutes to 2 hours, or until the tomatoes are very soft and slightly shrunken.
Increase the oven temperature to 400 degrees.
Place the baguette slices on a baking sheet, drizzle with olive oil and bake until golden brown, about 10 minutes. Rub the crostini with garlic and top each with a roasted tomato.