Preheat the oven to 425°F (220°C). Line a baking sheet with parchment paper.

In a large bowl, toss the halved Brussels sprouts with 2 tablespoons of olive oil, salt, and pepper. Spread them out on the prepared baking sheet in a single layer. Roast in the oven for 20-25 minutes, or until crispy and golden brown, stirring halfway through.

While the Brussels sprouts are roasting, bring a large pot of salted water to a boil. Add the orecchiette and cook according to package instructions until al dente. Reserve 1/2 cup of pasta water, then drain the pasta.

In the same pot, heat the remaining tablespoon of olive oil over medium heat. Add the minced garlic and red pepper flakes (if using) and sauté for about 1 minute until fragrant.

Add the cooked orecchiette, broccolini, and reserved pasta water to the pot. Stir to combine and cook for an additional 2-3 minutes, allowing the broccolini to soften slightly.

Remove from heat and stir in the roasted Brussels sprouts, Parmesan cheese, and lemon juice. Adjust seasoning with salt and pepper as needed.

Serve immediately, garnished with fresh parsley and additional Parmesan if desired.