Preheat the oven to Gas 7, 220°C, fan 200°C. Peel the pumpkin and then using a large sharp knife, cut into generous-sized wedges, discarding the seeds as you go.
Put the wedges into a roasting pan and drizzle over a little olive oil, and toss the pumpkin pieces in it with your hands. Add a head of garlic that's been sliced horizontally, a handful of fresh sage leaves and a sprinkling of salt and freshly ground black pepper.
Roast for 30 minutes or until the pumpkin flesh is soft and the edges are beginning to brown.