Preheat your oven to 425°F (220°C). This high temperature is essential for achieving that crispy finish.
In a large mixing bowl, combine the cauliflower florets with olive oil, salt, black pepper, garlic powder, smoked paprika, and cornstarch. Toss everything together until the florets are evenly coated.
Spread the coated cauliflower in a single layer on a baking sheet lined with parchment paper. Ensure that the florets are not overcrowded to allow for proper airflow and crispiness.
Roast in the preheated oven for 25 to 30 minutes, turning the florets halfway through to ensure even browning. The cauliflower should be golden brown and crispy on the edges when done.
If using, sprinkle the nutritional yeast or grated parmesan over the cauliflower in the last five minutes of roasting for added flavor.
Once roasted, remove the cauliflower from the oven and let it cool for a few minutes. Garnish with fresh parsley before serving.