Preheat the oven to 200°C, fan 180°C, gas 6. In a large roasting tin, toss together the peppers, courgette, aubergine, red onion, oregano and olive oil. Put in the oven and roast for 25-30 minutes, shaking the tin occasionally.
Meanwhile, put the pasta in a large saucepan and cover with salted boiling water. Bring back to the boil, then cook for 8-10 minutes until just al dente. Drain, and then mix well with the chopped tomatoes and Greek-style yogurt.
Gently toss the vegetables through the pasta and then spoon into a 20cm square ovenproof dish. Sprinkle over the cheese and then bake in the oven for 20 minutes until bubbling and the cheese is brown.