Preheat the oven to 400 degrees. Coat a shallow baking dish or ovenproof skillet with a thin layer of olive oil.
Blanch the Brussels sprouts in a large pot of boiling water for 4 minutes. Drain and when cool enough to handle, trim the ends, and halve lengthwise.
Transfer the sprouts to a large bowl, add the olive oil, garlic, 1/2 teaspoon salt, and 1/4 teaspoon black pepper and toss to coat. Add the parmesan cheese and toss to coat.
Transfer the sprouts to the prepared pan and bake for 8 to 10 minutes, until golden brown. Serve with crushed red pepper flakes on top or on the side.