Preheat oven to 220 C / Gas 7.
Place the pumpkin, carrots and onion onto a roasting tin and toss with vegetable oil, placing the sage leaves amongst the chunks of vegetable.
Roast in the oven for about 40 minutes, until soft but not charred.
Remove from the oven and discard the sage leaves.
Place the roasted vegetables into a large saucepan and cover with the stock.
Bring to the boil and using a stick blender, puree until smooth.
Season with salt and pepper