Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
In a small bowl, whisk together the Dijon mustard, curry powder, honey, and half of the olive oil until the glaze is smooth and emulsified.
Place the chicken breast on one side of the prepared baking sheet and brush it generously with half of the curry-mustard glaze.
Chop the bell pepper and carrot into bite-sized pieces, then place them in a bowl with the broccoli florets.
Toss the vegetables with the remaining olive oil, sea salt, black pepper, and garlic powder until evenly coated.
Spread the seasoned vegetables in a single layer on the other side of the baking sheet around the chicken.
Roast for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with slightly charred edges.
Remove from the oven, drizzle the remaining curry-mustard sauce over the chicken, and serve immediately.