Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized cubes and place them in a large mixing bowl along with the broccoli and cauliflower florets.
In a small jar or bowl, whisk together the extra virgin olive oil, lemon juice, minced garlic, red pepper flakes, sea salt, and black pepper.
Pour the lemon-garlic dressing over the chicken and vegetables, tossing thoroughly with your hands or a spatula to ensure every piece is well-coated.
Spread the mixture in a single layer on the prepared baking sheet, making sure not to crowd the pan so the vegetables roast rather than steam.
Roast for 18 to 22 minutes, tossing the ingredients halfway through, until the chicken is cooked through and the vegetables have golden, crispy edges.
Remove the pan from the oven and immediately sprinkle the grated parmesan cheese over the hot chicken and vegetables.
Serve immediately while the meal is hot and the flavors are vibrant.