Preheat the oven to 425°F (220°C) and line a large baking sheet with parchment paper.
Cut the cauliflower into uniform florets and dry them thoroughly with a clean kitchen towel or paper towels.
Place the florets in a large bowl, add the olive oil, garlic powder, paprika, cumin, salt and black pepper, and toss by hand until every floret is fully coated.
Spread the florets in a single layer on the baking sheet with space between them — no overlapping.
Roast for 20 minutes without stirring, then stir and roast for 10 to 15 minutes more, until the edges are crisp and caramelized and the centers are tender.
If using, sprinkle the grated Parmesan over the cauliflower in the final minutes of roasting so it melts and turns golden.
Rest for 2 to 3 minutes, scatter over the fresh parsley, and serve with the lemon wedges.