Preheat oven to 400°F. Line a large rimmed baking sheet with parchment paper.
Toss cauliflower, butter, oil, Parmesan, garlic, salt and pepper in a large bowl until coated. Spread in a single layer on the prepared baking sheet. Roast, stirring halfway through, until tender and golden, 35 to 40 minutes.
Sprinkle with parsley. Garnish with additional Parmesan, if desired.
