Preheat your oven to 425°F (220°C).
Wash the broccoli heads under cold water and pat them dry. Cut into bite-sized florets.
Thinly slice the peeled garlic cloves.
In a large mixing bowl, combine broccoli florets, sliced garlic, olive oil, salt, and black pepper. Toss to coat.
Spread the broccoli and garlic on a large baking sheet in a single layer.
Roast for about 20 minutes, tossing halfway through.
Add Parmesan cheese and pecans, and roast for an additional 5 minutes until cheese is melted.
Drizzle with lemon juice and serve warm.