Add the balsamic vinegar, two tablespoons olive oil, maple syrup, orange zest, orange juice, thyme, and sage to a medium bowl. Season with salt and black pepper, to taste, and whisk to combine. Set aside.
Place the chicken breasts in a gallon-size freezer bag and pour the balsamic mixture on top. Squeeze out excess air and seal bag tightly. Carefully turn bag to ensure the chicken is evenly coated and marinate at room temperature for 30 minutes or place in the refrigerator for one hour to overnight. Turn bag occasionally while marinating for more even distribution of flavors.
To prepare, place top oven rack in center position and pre-heat oven to 400°F. Line a large, rimmed baking sheet with parchment paper or a Silpat® baking mat and set aside.
Remove chicken from marinade and place on prepared baking sheet and generously season with additional salt and black pepper, if desired. Discard bag and any remaining marinade.
Toss the sweet potatoes, broccoli, and red onion in a large bowl with the remaining olive oil, onion powder, and garlic powder. Season with salt and black pepper, to taste, and arrange the seasoned veggies around the chicken breasts in a single layer without overcrowding.
Place the baking sheet in the preheated oven to roast until the chicken is fully cooked through and the veggies are fork-tender and starting to brown, approximately 20-25 minutes. Remove from oven and cool slightly before serving.