Heat the oil with garlic in a large frying pan and cook until fragrant, about 1 minute. Add lemon slices and sauté for 3-4 minutes until lightly golden on both sides.
In the meantime, heat 7 quarts of water to boiling and add 2 tablespoons of salt. Add broccoli florets and cook 3-4 minutes. Drain broccoli florets with a slotted spoon keeping the water and transfer to the pan. Cook over high-heat for 3-4 minutes until well roasted. Season with salt and pepper to taste.
In the same water you used to cook broccoli, cook Tortelloni according to package instructions and drain, reserving ½ cup of the pasta cooking water. Add Tortelloni to the pan and stir gently, adding pasta water a little at a time if you need to loosen the sauce. Divide among plates. Sprinkle with grated Pecorino and more pepper and serve.