Pre-heat the oven to 200°C.
Place all the vegetables in a large roasting dish and drizzle over 50ml of the olive oil and the balsamic vinegar. Add seasoning and the sugar and toss well to combine. Roast for 20-25 minutes until soft and starting to colour and caramelise.
Meanwhile, place the couscous in a large heatproof bowl. Bring the stock to a boil in a saucepan over a medium-high heat. Pour the stock over the couscous then cover the bowl with clingfilm. Allow to sit for 5-6 minutes until the stock has been absorbed.
Remove the clingfilm and fluff the grains with a fork. Remove the vegetables when ready. Spoon the couscous into serving bowls and top with the vegetables. Serve immediately.