Preheat oven to 425 degrees Fahrenheit. Five minutes before baking, place your half sheet pan (with nothing on it) into the oven to preheat.
In a large bowl, add your frozen broccoli florets. Drizzle olive oil and sprinkle red pepper flakes, garlic powder, salt, and pepper over top. Toss to evenly coat.
Carefully, using oven mitts, remove your preheated baking sheet from the oven. Lightly spray with cooking spray, or line with a sheet of parchment paper. Pour prepared broccoli onto baking sheet and spread out evenly. Sprinkle parmesan cheese over broccoli florets.
Bake for about 20-22 minutes, or until broccoli is lightly browned around the edges and is crisp-tender (can pierce through with a fork with little resistance).
Why preheat your sheet pan? When pouring frozen broccoli onto a preheated sheet pan, the veggies instantly begin to defrost. Any water released from the broccoli will quickly evaporate, instead of slowly forming puddles for your broccoli to sit in (making it soggy and mushy).
Red pepper flakes can be omitted for a mild flavor.
Leftover cooked broccoli will keep for 3 to 5 days in a tightly sealed container in the refrigerator.