Heat the oven to 190C/170C fan or GM6. Line a large or 2 smaller baking trays with baking paper.
Wash the outside of the butternut squash and peel the carrots and parsnips. Chop the squash into large pieces, and the parsnips and carrots into smaller pieces. (Its quicker to take the butternut squash skin off once cooked).
Toss the vegetables in 1 tablespoon of the olive oil, either in a large food bag or big bowl. Season with salt and pepper and spread out in an even layer on the baking trays.
Place in the oven and roast for 45 minutes. After 45 minutes, clear a small space at the edge of one of your trays and spread out the pumpkin seeds. Roast for a further 15 minutes.
Remove the vegetables from the oven, and carefully scrape the flesh of the butternut squash away from the skin with a spoon and fork, and throw away the skin. Reserve the pumpkin seeds in a small bowl for garnish.
Heat the remaining tablespoon of olive oil in a large saucepan, and add the turmeric and ginger.
Tip the roasted vegetables into the pan with the turmeric and ginger, and stir. Add the vegetable stock and bring up to a low simmer. Check the carrots are tender, if not, simmer with the lid on for a further 5 minutes.
Blend the soup (I use a stick blender) and serve in bowls, topped with the pumpkin seeds and a large pinch of sumac.