On a large baking sheet, toss the cauliflower florets with 2 tablespoons of olive oil, salt, and pepper. Spread them out into a single layer.
Roast the cauliflower in the oven for about 25 minutes, or until golden brown and tender, flipping halfway through. Add the minced garlic in the last 5 minutes of roasting.
While the cauliflower is roasting, bring a large pot of salted water to a boil. Cook the pasta according to package instructions until al dente. Drain, reserving about 1 cup of pasta water.
In a blender or food processor, combine the roasted cauliflower (and garlic), vegetable broth, heavy cream, and nutmeg. Blend until smooth and creamy.
In the pot used for the pasta, combine the creamy cauliflower mixture with the drained pasta, and stir in the grated Parmesan cheese. If the sauce is too thick, add reserved pasta water a little at a time until reaching your desired consistency.
Taste and adjust seasoning with salt, pepper, and red pepper flakes if desired.
Serve immediately, garnished with fresh parsley and an extra sprinkle of Parmesan cheese.
Notes
For a vegan option, substitute heavy cream with plant-based cream and Parmesan with nutritional yeast.