Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Chop the chicken breast into bite-sized cubes and slice the bell pepper and red onion into thin strips.
Place the chicken cubes, broccoli florets, bell pepper strips, and red onion in a large mixing bowl.
In a small jar or bowl, whisk together the olive oil, lemon juice, dried thyme, dried rosemary, sea salt, and black pepper.
Pour the herb dressing over the chicken and vegetables, tossing thoroughly to ensure every piece is evenly coated.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the pieces aren't too crowded.
Roast for 20-25 minutes, or until the chicken is cooked through and the vegetables are tender with slightly charred edges.