Preheat your oven to 220°C (425°F) and line a large baking sheet with parchment paper.
Wash and thoroughly dry the broccoli, then cut it into uniform florets about 2-3 inches wide for even roasting.
In a mixing bowl, toss the broccoli florets with olive oil, thinly sliced garlic, salt, and pepper, making sure each piece is well coated.
Spread the coated broccoli in a single layer on the prepared baking sheet, placing garlic slices evenly over the top.
Roast in the oven for 20-25 minutes, shaking the pan halfway through, until the edges are crispy and golden brown, and the garlic is fragrant and jammy.
Remove the tray from the oven. Immediately sprinkle the hot broccoli with freshly grated Parmesan cheese and squeeze lemon juice over if using.
Toss gently to distribute the cheese and flavors, allowing the cheese to melt into the hot florets.
Let sit for 2-3 minutes to allow the cheese to melt fully and the flavors to meld together.
Serve immediately while hot, garnished with extra Parmesan or a final squeeze of lemon if desired.