Preheat your oven to 400°F. Rinse Brussels sprouts, trim ends, and cut in half. Peel and dice butternut squash.
Cook pasta in salted boiling water until al dente, about 8-10 minutes. Reserve 1/2 cup pasta water before draining.
Toss Brussels sprouts and butternut squash with olive oil, salt, pepper, and red pepper flakes. Spread on a baking sheet and roast for 25-30 minutes.
In a skillet, heat remaining olive oil, sauté garlic for 1 minute. Add roasted vegetables and cooked pasta, toss with reserved pasta water and Parmesan cheese.
Garnish with parsley and serve.