Preheat the oven to 425ºF (218ºC) and line a sheet pan with parchment paper.
Add the oil and ranch seasoning to a large bowl and stir well until well combined.
Transfer the broccoli to the bowl, and fold together with the oil and seasoning until the broccoli is evenly coated.
Spread the seasoned broccoli on the parchment-lined baking sheet.
Roast in the preheated oven for 15-17 minutes, or until soft with browned edges. Stir the broccoli halfway through to ensure even cooking.
Remove from the oven and sprinkle the parmesan cheese on top.
Return to the oven for 1-2 minutes to melt the cheese, then remove and serve immediately.
Notes
Air fryer: Cook in an air fryer that has been preheated to 375ºF (190ºC) for 8-12 minutes, shaking the basket halfway through. The broccoli is done once tender with crispy edges. Storing: Add any leftovers to an airtight container and store for up to 3 days. Reheat in the microwave or in the oven or air fryer until heated through.