Toss the diced aubergine in a little oil with some salt and pepper, and spread it out in a single layer on a baking tray. Roast at 180°C (Gas Mark 4 / 350°F) for around 25 minutes, or until the aubergine is soft and juicy.
Meanwhile, boil the brown rice in plenty of water until cooked to your liking (around 20 minutes). Drain, and transfer the rice to a large mixing bowl.
To the rice, add the remaining ingredients, including the roasted aubergine. Mix well to combine, and serve warm.