1.Preheat oven to 220°C (200°C fan-forced). Line an oven tray with baking paper.
2.Combine oil, lemon juice, sugar and pepper in a large bowl. Add parsnip; toss to combine. Transfer the parsnip mixture to prepared tray. Roast for 20 minutes.
3.Meanwhile, bring a medium saucepan of water to the boil. Trim off the bases of the brussels sprouts. Peel off outer dark green leaves. Blanch in boiling water for 1 minute; drain. Cut any of the large sprouts in half.
4.Remove parsnips from the oven; turn them over. Add brussels sprouts; return to oven for a further 30 minutes, or until browned lightly. Serve vegetables sprinkled with parsley.
Not suitable to freeze. Brussels sprouts suitable to microwave.Note