1. First of all wrap the eggplant, bell peppers and onions separately in tinfoil and put them on an oven rack.
2. Roast the vegetables in a preheated oven at 428°F (220°C) for about 45 minutes. In the end turn off the oven but leave the vegetables in it for another 30 minutes until totally soft.
3. Then take the vegetables out of the oven and carefully remove the tinfoil. Peel away the skin on the bell peppers and remove the stems and seeds inside. Slice the bell peppers and the other vegetables into portions.
4. Sprinkle a baking dish with some olive oil and a dash of pepper and salt. Add the vegetables. Drizzle with more olive oil, the white wine vinegar and extra pepper and salt.
5. Place the dish in the fridge for a couple of hours until chilled and marinated, preferably overnight. Serve at room temperature.