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 cubes and place them in a large mixing bowl.
Chop the broccoli into small florets, slice the zucchini into half-moons, and dice the red bell pepper into 1-inch pieces.
In a small bowl, whisk together the olive oil, lemon juice from the half lemon, minced garlic, rosemary, thyme, sea salt, and black pepper.
Pour the lemon-herb marinade over the chicken and vegetables, tossing well to ensure every piece is thoroughly coated.
Spread the mixture onto the prepared baking sheet in a single, even layer to ensure the ingredients roast properly rather than steaming.
Roast in the center of the oven for 20 to 22 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender.