Preheat the oven to 200°C/gas mark 6. In a large roasting tin, toss together the peppers, courgette, aubergine, red onion, oregano and olive oil. Roast in the oven 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, then mix well with the chopped tomatoes, mixed dried herbs, yogurt and tuna.
Gently toss the vegetables through the pasta and spoon into a 20cm square ovenproof dish. Sprinkle over the cheese, then bake in the oven for 20 minutes until bubbling and the cheese is brown.