Preheat the oven to 400 degrees Fahrenheit. Set an oven rack in the center of the oven and line a half sheet pan with foil to facilitate cleanup.

Remove the leaves from the cauliflower head and place the head securely on a cutting surface. With a large knife, slice in half. Carefully remove the center stem and set aside. Cut the florets into pieces about the size of your thumb. Cut the stem into one-​inch cubes.

Combine the olive oil and garlic in a large bowl. Add the cauliflower and gently toss to allow the oil and garlic to coat the cauliflower evenly.

Combine the salt, red pepper flakes, parsley, and Parmesan in a small bowl. Mix together well. Sprinkle half of the seasonings evenly over the cauliflower and gently mix to coat.

Spread the cauliflower over the baking sheet, trying to keep it as close to a single layer as possible. Using a spoon or your fingers, sprinkle the remaining seasonings from a height of 12 inches over the cauliflower. which will help distribute the seasonings more evenly.

Bake for 20 to 30 minutes, gently turning the cauliflower halfway through with a spatula. When the cauliflower begins to turn golden and tender, remove from the oven and serve.