Preheat oven to 400 degrees. Toss the broccoli florets and garlic on a rimmed baking sheet and drizzle with a generous amount of olive oil. Season well with salt and pepper. Roast for 20 minutes, until broccoli is tender and caramelized. The tips of the “trees” should be nicely browned and crisp. In a small bowl, whisk together the 2 tbsp olive oil, Parmesan, red pepper flakes, lemon juice, and lemon zest. Toss with the broccoli and serve.