Preheat the oven to 400 degrees. Line a baking sheet with parchment paper.
Pour 2 tablespoons of olive oil into a 9 x 12-inch baking dish. Cut the tomatoes in half, place in the dish, cover with another 2 tablespoons oil, salt, pepper, and crushed red pepper flakes. Scatter the garlic on top of the tomatoes. Roast for 20 minutes. Leave the oven on.
Cut the baguettes into ½-inch slices. Place on the prepared baking sheet. Brush with oil and season lightly with salt and pepper. Bake for 6-8 minutes or until golden.
Drain and rinse the beans. Add to the tomatoes while still warm and mash with a fork. Let sit while the baguette slices toast. Stir the basil into the tomato mixture. Taste and add more salt and pepper, if desired.
Transfer tomatoes to a serving bowl and serve with the crostini. Drizzle with extra olive oil, if desired.