Cut each tomato into 8 and thickly slice the pepper quarters. Place in a roasting tin with the onion, then drizzle with the oil and season well. Tear some of the sage into pieces and sprinkle over the vegetables. Roast in a preheated oven, 200°C (400°F), Gas Mark 6, for 40–45 minutes until softened.
Meanwhile, cook the rice in a saucepan of boiling water for 15 minutes until only just cooked. Drain, rinse in cold water and drain again well. Mix the rice into the cooked tomatoes and peppers, then cover with foil. Allow to cool and chill until required.
When ready to serve, reheat in a preheated oven, 180°C (350°F), Gas Mark 4, still covered with foil for 20 minutes until piping hot. Stir well then spoon into bowls and sprinkle with the remaining sage leaves. Serve with warm ciabatta or herb bread.