Preheat the oven to 400°F (200°C). In a bowl, toss the halved cherry tomatoes with olive oil, salt, and pepper. Spread them on a baking sheet and roast for 20 minutes until soft and slightly caramelized.

In a large pot, bring salted water to a boil. Add the spaghetti and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain the pasta.

In a blender, combine basil leaves, parmesan cheese, olive oil, pine nuts, garlic, salt, and pepper. Blend until smooth, adding reserved pasta water as needed to reach desired consistency.

In the pot with the drained pasta, add the pesto and roasted tomatoes. Toss to combine, adding more pasta water if necessary. Serve warm, garnished with additional parmesan cheese if desired.