For the Pasta, combine all ingredients in a food processor and blitz until dough comes together. Transfer to lightly floured work surface and knead until smooth. Wrap in cling film and set aside to rest for 25 minutes.
Roll rested dough through pasta machine to 2mm thickness to a length of 120cm x 10cm. Cut in half and place two sheets of pasta next to each other to create 1 large sheet 20cm x 60cm. Cover with a clean tea towel and set aside.
For the Roasted Leeks, place leek and garlic onto a baking tray lined with baking paper. Drizzle with olive oil and season with salt and pepper. Roast in the oven until tender, but still holding shape, about 35-40 minutes. Remove from pan, slice into 3cm batons and set aside.
For the Ricotta, place all ingredients, except vinegar, into a saucepan over medium heat and bring to the boil. Add vinegar and stir through gently. Remove from the heat and allow to sit for 10 minutes. Strain through a sieve lined with cheesecloth until just the soft curds remain, about 8-10 minutes. Transfer curds (ricotta) to a bowl and set aside.
For the Pumpkin Filling, place pumpkin, butter and milk into a saucepan over medium heat and cook until pumpkin is completely soft, about 6-8 minutes. Add reserved ricotta and stir well until smooth. Remove from heat and pass through a fine sieve into a clean bowl. Add chopped parsley and season well. Set aside.
Bring large saucepan of salted water a simmer over medium heat.
Spread Pumpkin Filling onto each pasta sheet leaving a 2 cm border along the length edges of the pasta. Roll up gently but firmly, from the long side, into a log and cut in half. Wrap each log tightly in cling film and secure ends.
Place logs into simmering water and cook for 12 minutes. Remove from water and carefully unwrap from cling film. Cut each log into 5cm lengths.
For the Sage Butter Sauce, heat 50g butter in a large fry pan over medium heat. When melted, place cut rotolo pieces into the pan standing upright. Add sage leaves and baste with the butter until brown and crispy, about 6-8 minutes. Remove from heat and set aside in the frypan, keeping warm.
Meanwhile, for the Cauliflower Puree, place cauliflower, 30g of the butter and milk into a medium saucepan over medium heat. Cook, stirring occasionally, until cauliflower is soft and liquid has evaporated. Add grapeseed oil and remaining 20g butter. Use a stick blender to blend to a smooth puree. Season and set aside.
For the Cauliflower Pangratatto, heat butter and oil in large fry pan over medium heat. Add grated cauliflower and fry until brown and crisp. Remove cauliflower and drain on paper towel. Season and set aside.
To serve, divide Cauliflower Puree between serving bowls. Top with 3 pieces of Roasted Leek, alternating with 3 rotolo. Sprinkle with Cauliflower Pangratatto and spoon over butter and sage leaves from the rotolo fry pan. Sprinkle with chopped parsley.