Place the cherry tomatoes on a baking sheet, then mix together with the oil and season. Cook under a preheated medium grill for 5 minutes or until beginning to brown.
Meanwhile, cook the pasta in a large saucepan of salted boiling water according to the pack instructions until al dente. Drain, reserving a little of the cooking water, and return to the pan. Stir through the pesto and mascarpone, adding a little cooking water to loosen if needed.
Gently stir in the tomatoes and season. Spoon into serving bowls and serve with the pine nuts scattered over.