Preheat oven to 200 °C. Prepare the vegetables. Remove the skin from the pumpkin and kumara and cut into 1.5cm chunks. Peel and thickly slice the carrots into rings. Cut the red onion into small wedges. Place on a tray. Toss 2 Tbsp of olive oil through the vegetables. Roast for 20-25 minutes, until vegetables are tender.