Preheat the oven. Place the rack in the middle position for even roasting and heat the oven to 230°C / 450°F.
Prepare the cauliflower. Remove the outer leaves and trim the stem so the head can rest flat on the cutting board. Cut the cauliflower in half, then slice each half again to make four even wedges. From each wedge, trim out the core and gently pull the florets apart by hand into medium bite-size florets (about 3-4 cm / 1.5 in). This way, they keep their natural shape and look neat once roasted.
Season. Place the florets in a large bowl, drizzle with olive oil, and toss until evenly coated. In a small bowl, mix the garlic powder, smoked paprika, salt, and black pepper. Sprinkle the seasoning over the cauliflower and toss again to coat. Finally, add the grated Parmesan and give it one last toss so it clings to the oiled florets.
Arrange. Lightly oil a large baking sheet, then spread the florets in a single layer. Leave a bit of space between them – if they’re too close together, they’ll steam instead of roast.
Roast. Place in the oven and roast until golden, about 25-30 minutes.
Serve. Take the cauliflower out of the oven, sprinkle it with chopped parsley, and serve right away while it’s still hot and the edges are crisp.