Rub the peppers with a little oil, and place them whole on a baking tray. Roast at 190°C (Gas Mark 5 / 375°F) for around 45 minutes, turning them over half way. They should be very soft and slightly charred.
Immediately transfer the peppers to a plate, and cover tightly with cling film (alternatively you could put the peppers in a tightly sealed food bag). Set aside for a few minutes.
Boil the pasta until al dente.
When the peppers have sat for 5 minutes or so, gently peel off the skin and remove the seeds. Place the flesh in a mini food processor, and blitz until smooth.
When the pasta is ready, drain it and add the roasted red pepper purée. Season to taste, and transfer to a baking dish (either two individual dishes, or one larger dish).
Add a few small dollops of ricotta to the top of each dish, and sprinkle over the grated cheddar. Bake at 190°C (Gas Mark 5 / 375°F) for around 30-40 minutes, until the cheese has melted and crisped up to your liking.
Serve topped with fresh herbs.