Preheat oven to 400 degrees F. Lightly oil a baking sheet.
In a small bowl, whisk together 3 tablespoons olive oil, honey, garlic and dijon mustard. Season with salt and pepper to taste. Combine half the honey garlic mixture and chicken breasts in a gallon size ziplock bag. Shake to coat the chicken well and then let marinate while cutting the brussels sprouts and sweet potatoes.
Place brussels sprouts (cut side down) and sweet potatoes in a single layer onto the prepared baking sheet. Drizzle with a little olive oil and season with salt and pepper. Top with the chicken in a single layer and pour the rest of the marinade mixture over the veggies and chicken.
Put in the preheated oven and roast until the chicken is completely cooked through (internal temperature of 165 degrees F) and the brussels sprouts and sweet potatoes are brown and caramelized.
While the dinner is baking, pour the remaining marinade in a small saucepan and bring to a boil. Cook for 2 minutes or until slightly thickened.
Once the sheet pan dinner is cooked, turn the oven to broil, and cook for 2-3 minutes, or until chicken is caramelized and veggies are a golden brown.
Remove from oven and baste everything with the marinade from the saucepan. Enjoy!