Prepare the oven: Heat your oven to 425°F (220°C). Cover a large rimmed baking sheet with parchment paper or aluminum foil for easier cleanup.
Season the cauliflower: Place the cauliflower florets in a large mixing bowl. Add the olive oil, Old Bay seasoning, chili pepper, and black pepper. Toss thoroughly until the seasoning and oil coat the cauliflower evenly.
Arrange for roasting: Transfer the seasoned cauliflower to the prepared baking sheet. Spread the pieces into a single layer, making sure they aren't overcrowded. This helps the edges become nicely browned and crisp.
Roast until golden: Bake for approximately 25–30 minutes, turning the cauliflower pieces halfway through cooking. Continue roasting until the florets are tender and the edges are golden brown.
Add the cheese: Remove the baking sheet from the oven and sprinkle the cheddar and Parmesan evenly over the roasted cauliflower. Return it to the oven for about 5 minutes, or until the cheese has completely melted and begins to bubble.
Serve: Let the cauliflower cool for a minute or two, then serve immediately while the cheese is warm and gooey and the roasted edges are still crisp.
