Preheat oven to 475 degrees F. Line a baking sheet with Reynolds Wrap® Aluminum Foil. Spread the broccolini on the baking sheet and drizzle with olive oil.
Using tongs, gently toss the florets in the oil to combine. Cut the head of garlic in half, and place the exposed garlic in some of the drizzled olive oil. Turn the garlic-exposed side up on the baking sheet and sprinkle everything with red pepper flakes.
Roast for 20-25 minutes until the broccolini is just slightly crispy.
Remove the baking sheet from oven and squeeze juice from the the fresh lemon on top of the broccolini. Adjust seasoning and add grated Parmesan cheese. Transfer the broccolini to a serving platter with the halved garlic heads. Remove the aluminum foil from the baking sheet and discard for easy cleanup. Serve immediately.