Preheat the oven to 220°C/gas mark 7. Place the sausages, butternut squash and aubergine on a large baking tray in a single layer. Drizzle over the olive oil and sprinkle with smoked paprika, then roast in the oven for 15 minutes.
Turn the vegetables and sausages, add the tomatoes and roast for a further 10 minutes, until the vegetables are tender and lightly charred at the edges and the sausages are cooked through.
Meanwhile, put the couscous in a heatproof bowl and pour over enough boiling water from the kettle to just cover. Cover the bowl with clingfilm and allow to stand for 10 minutes until the water has been absorbed by the couscous.
Fluff up the couscous with a fork, then season with freshly ground black pepper and stir in the parsley. Cut the sausages into chunks and put in a large bowl. Add to the couscous with the roasted vegetables and any juices from the baking tray. Toss everything together, divide between 4 plates and serve.