Heat oven to 200C/180C fan/gas 6. Put the squash and garlic on a baking tray and drizzle with the olive oil. Roast for 35-40 mins until soft. Season.
Cook the pasta according to pack instructions. Drain, reserving the water. Use a stick blender to whizz the squash with 400ml cooking water. Heat some oil in a frying pan, fry the sage until crisp, then drain on kitchen paper. Tip the pasta and sauce into the pan and warm through. Scatter with sage.