Preheat the oven to 400°F (200°C or 190°C for fan ovens).
Spread the prepared vegetables on a large baking sheet.
Drizzle with 2 tablespoons of the oil and toss to coat.
Roast the vegetables for 20 minutes, then remove from the oven and carefully turn the vegetables in the oil. Drizzle on the remaining tablespoon of oil if the vegetables seem at all dry.
Return the vegetables to the oven and cook for a further 15 - 20 minutes until nicely roasted but not too brown.
(At this point the vegetables can be cooled and chilled for 3 to 4 days if you want to make them ahead of time.)
Lower the heat in the oven to 350°F (175°C or 160°C for fan ovens).
Warm the passata or tomato sauce in a medium saucepan over low heat.
Stir the pesto, oregano and pepper into the tomato sauce and continue to heat, stirring occasionally.
Meanwhile, cook the pasta in a large pan of boiling salted water according to package directions. When cooked to al dente, drain and return the pasta to the cooking pan.
Stir the passata or tomato sauce into the pasta in the large saucepan, along with the roasted vegetables.
Place half the pasta, sauce and vegetable mixture in a large casserole.
Sprinkle with half the cheese.
Cover with the remaining pasta and vegetables.
Sprinkle with the remaining cheese.
Place the casserole in the oven and bake for 15 to 20 minutes or until the cheese is melted and golden on top.