Preheat your oven to 425°F (220°C) and line a large baking sheet with parchment paper.
Trim the woody ends from the brussel sprouts and remove any discolored outer leaves.
Cut each sprout in half lengthwise (quarter very large ones to ensure even cooking).
Place the prepared brussel sprouts in a large mixing bowl.
Drizzle the olive oil over the brussel sprouts.
Add the minced garlic, salt, and black pepper.
Toss thoroughly to ensure each sprout half is coated with oil and seasonings.
For extra flavor, add optional red pepper flakes now if using.
Transfer the seasoned brussel sprouts to your prepared baking sheet.
Arrange them in a single layer with the cut sides facing down, ensuring they're not overcrowded. Use a second baking sheet if needed.
Place the baking sheet in the preheated oven.
Roast for 15 minutes without disturbing them.
After 15 minutes, check for browning. The cut sides should be turning golden brown and caramelized.
Remove the baking sheet from the oven.
Sprinkle the grated parmesan cheese evenly over the brussel sprouts.
Return to the oven for an additional 3-5 minutes, until the cheese is melted and golden.
Remove from the oven and immediately drizzle with fresh lemon juice if using.
Use a spatula to gently transfer to a serving dish, making sure to scrape up any crispy cheese bits from the pan.
Serve hot for the best texture and flavor experience.