01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large bowl, toss halved Brussels sprouts with olive oil, sea salt, black pepper, and optional garlic powder and chili flakes until evenly coated.
03 - Spread the Brussels sprouts cut-side down in a single layer on the prepared baking sheet.
04 - Roast for 20 to 25 minutes, flipping halfway through, until edges are golden brown and crisp.
05 - Remove from oven and sprinkle with Parmesan, parsley, and lemon zest if desired. Serve immediately.