Preheat your oven to 425°F (220°C).
Wash and cut the broccoli into florets, ensuring each piece has about an inch of stem attached.
In a mixing bowl, combine broccoli florets with olive oil, 1 teaspoon of kosher salt, black pepper, and crushed red pepper flakes. Toss until well-coated.
Spread the seasoned broccoli evenly on the baking sheet in a single layer.
Roast the broccoli for about 20 minutes, or until edges are crispy and stems are tender.
While the broccoli is roasting, melt the unsalted butter in a small bowl. Mix in panko, Cheddar, Parmesan, and remaining teaspoon of kosher salt.
After 20 minutes, remove broccoli from the oven and sprinkle the cheesy mixture over it.
Return the baking sheet to the oven and roast for an additional 5-7 minutes, until cheese is bubbly and golden brown.
Let cool for a couple of minutes, then serve warm and enjoy!