Preheat your oven to 425°F (220°C). Toss the cauliflower florets with olive oil, salt, and pepper until well coated. Spread them out on a baking sheet in a single layer. Roast for 20-25 minutes, stirring halfway through, until the cauliflower is golden brown and tender.
While the cauliflower roasts, bring a large pot of salted water to a boil. Add the macaroni and cook according to package instructions until al dente (usually about 7-8 minutes). Drain the pasta and set aside.
In a medium saucepan over medium heat, combine the milk, softened cream cheese, garlic powder, onion powder, paprika, and cayenne pepper (if using). Stir continuously until the cream cheese melts and the mixture is smooth and warm. Gradually add the shredded cheddar cheese and half of the Parmesan cheese, stirring until melted and creamy. Season with salt and pepper to taste.
Add the cooked macaroni and roasted cauliflower to the cheese sauce. Stir gently to coat everything evenly with the cheesy goodness. If the sauce feels too thick, add a splash more milk to loosen it up.
For a bubbly, golden top, transfer the mac and cheese mixture to a greased oven-safe baking dish. Sprinkle the remaining Parmesan cheese on top and bake at 350°F (175°C) for 15-20 minutes until the cheese is melted and slightly browned. Alternatively, you can skip baking and serve straight from the stove for a quicker meal.
Sprinkle chopped fresh parsley over the top for a pop of color and fresh flavor. Serve warm and enjoy this creamy, comforting Roasted Cauliflower Mac And Cheese.