Cut the broccoli into florets that are all similar in size. Place the florets and the sliced garlic on a baking sheet, drizzle with 1/4 cup of olive oil, season with salt, pepper and a pinch of red pepper flakes (to taste).
Roast for 15-18 minutes, or until the edges of the broccoli are starting to brown.
Remove from oven and drizzle on 1 tablespoon olive oil, zest the lemon over the broccoli and add the parmesan cheese. Toss to coat.
Serve with lemon slices for each person to squeeze a lemon wedge over their broccoli to taste.