Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Pat the chicken breast dry with a paper towel to ensure a good sear, then cut it into uniform 1-inch bite-sized pieces.
Wash the broccoli and cut it into small florets, making sure they are completely dry so they roast instead of steam.
In a large mixing bowl, whisk together the olive oil, minced garlic, finely chopped rosemary, thyme, sea salt, and black pepper.
Add the chicken pieces and broccoli florets to the bowl and toss thoroughly until every piece is well-coated with the herb oil.
Spread the mixture in a single layer on the prepared baking sheet, ensuring there is space between the pieces for hot air to circulate.
Roast for 18 to 22 minutes, or until the chicken is cooked through and the broccoli edges are golden and slightly charred.
Remove from the oven and immediately squeeze the fresh lemon juice over the hot chicken and vegetables to brighten the flavors before serving.