Preheat the oven to 400F. On a parchment lined baking sheet, add the cauliflower, onion, garlic, parsnip and sliced potatoes, along with the salt, pepper and oregano. Drizzle with olive oil if desired. Place in the oven for 40 minutes, until the vegetables are tender.
Meanwhile, cook the pasta according to package directions, reserving at least 1 cup of pasta water.
Once roasted, add all of the vegetables to a blender with the sunflower seeds, plant-based milk, nutritional yeast, lemon juice and dijon.
Add the alfredo sauce to a pan with pasta water as needed to thin. Stir in the cooked alfredo pasta and enjoy immediately.