Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Trim the stems from the Brussels sprouts and slice them in half, then dice the chicken breast into bite-sized 1-inch cubes.
Place the chicken and sprouts on the prepared pan, drizzle with the olive oil, and sprinkle with sea salt, black pepper, garlic powder, and red pepper flakes.
Use your hands or a spatula to toss everything together until the ingredients are well-coated, then spread them out in a single layer.
Roast for 22-25 minutes, flipping the chicken and sprouts halfway through, until the chicken is golden and the sprouts are crispy.
While roasting, whisk the balsamic vinegar and honey together in a small bowl until smooth.
Remove the pan from the oven, drizzle the balsamic mixture over the chicken and sprouts, and toss to coat before serving warm.