Soften the garlic in 1 tbsp of the olive oil and leave to cool slightly. Put the mozzarella, butter, garlic, sage, lemon zest and juice into a food processor. Season and blend to a coarse paste, scraping down the sides with a spatula a few times. Transfer the paste to a sheet of parchment paper or cling film and roll into a cylinder. Chill for 30 mins or until firm enough to slice.
Heat oven to 200C/fan 180C/gas 6. Pour remaining oil into a roasting tin and heat in the oven for 5 mins. Meanwhile, using a small sharp knife, peel the pumpkin, remove the seeds and cut flesh into 2cm cubes. Toss it in the hot oil, and season if you wish. Roast for 25-30 mins, turning occasionally.
Cook the pasta according to pack instructions. Drain, return to the pan and tip in the pumpkin and parmesan. Slice or chop the mozzarella butter and toss into the hot pasta. Divide between 4 bowls, top with sage and serve.