Preheat the oven to 400F. Line a large baking tray with parchment paper.
Spread the squash into an even layer in the lined pan, drizzle with 1 tablespoon of the olive oil, and toss to coat. Roast for 25 to 30 minutes, or until tender (but not mushy) and beginning to caramelize, tossing at the halfway point.
Bring a large pot of water to a boil and add 1 tablespoon sea salt. Add the pasta and cook according to package instructions (you want the pasta to have a nice al dente bite to it). Drain the pasta, reserving 1 cup of the cooking water, and set aside.
Meanwhile, bring a medium pot of water to a boil. Add the cauliflower florets and boil for 7 minutes, or until very fork-tender. Strain off the water.
Add the boiled cauliflower florets, filtered water, cashews, nutritional yeast, vinegar, 1 teaspoon sea salt, and black pepper to a blender (do not use a food processor). Blend on high for 2 minutes, or until completely smooth and creamy. Set within reach of the stove.
Heat the remaining 1 tablespoon olive oil and the garlic in a large sauté pan over low heat. Cook for 2 minutes, or until soft and fragrant.
Stir in the cauliflower sauce, and simmer for 1 minute, or until warmed through.
Turn off the heat, add the pasta to the pan, and toss to coat. If a slightly thinner sauce is desired, add a bit of the reserved cooking water, one small splash at a time, as needed to thin. (Note: If you add cooking water, you'll need to increase the seasoning to accommodate.)
Taste and generously season with more sea salt and black pepper, if desired.
Divide the pasta between bowls and top with the roasted butternut squash and parmesan (if using). Serve immediately.