Preheat the oven to 200°C, fan 180°C, gas 6. Line a 30cm x 20cm baking tray with baking parchment.
To make the roll, melt the butter in a small pan. Add the flour and cook for 1 minute. Slowly add the milk and stir until it thickens. Simmer for 2 minutes. Pour into a large bowl and stir in 40g grated Italian hard cheese, half the sage and the egg yolks. Season with black pepper.
In a separate bowl, whisk the egg whites until soft peaks form, then fold into the mixture. Pour into the prepared baking tray and bake for 30 minutes.
Meanwhile, cook the squash to pack instructions. Mash with the remaining sage and the soft cheese.
Turn out the sponge onto a sheet of baking parchment and spread with the squash mixture. Roll up from the longest side and sprinkle with the remaining Italian hard cheese. Return the roll to the oven for 5 minutes, until golden. Garnish with the parsley to serve.