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 uniform 1-inch bite-sized pieces and chop the broccoli into small, even florets.
In a large mixing bowl, combine the chicken and broccoli with olive oil, sea salt, black pepper, and red pepper flakes, tossing until every piece is well-coated.
Spread the mixture in a single layer on the prepared baking sheet, making sure not to overcrowd the pan so the broccoli can crisp up properly.
Roast for 18-20 minutes, or until the chicken is cooked through and the broccoli edges are beautifully charred and tender.
While the pan is still hot, remove it from the oven and immediately toss the mixture with the minced garlic, lemon juice, and lemon zest.
Transfer to a plate and serve immediately, enjoying the bright citrus notes and the savory aroma of the fresh garlic.