Preheat your oven to 400 degrees Fahrenheit. This is important to ensure that your chicken cooks evenly and your vegetables get that perfect roast.
While the oven is heating up, grab a small bowl and mix together the dried dill, dried parsley, garlic powder, onion powder, fine sea salt, and ground black pepper. This blend will serve as your ranch seasoning.
In another bowl, combine the mayonnaise, almond milk, and finely sliced scallions. Stir in half of the ranch seasoning mixture until everything is well incorporated. Set it aside for now.
In a large mixing bowl, toss together the red onion, diced sweet potato, diced red bell pepper, broccoli florets, and avocado oil. Sprinkle the remaining half of the ranch seasoning over the vegetables and mix until they’re well coated.
Spread the vegetable mixture evenly onto a rimmed baking sheet. Place it in the preheated oven and bake for twenty minutes. This initial roasting will bring out their sweetness.
While the vegetables are baking, take the chicken breasts and add them to the mixing bowl you used for the vegetables. Pour in about one third of the ranch dressing you prepared earlier. Toss well to coat the chicken and let it marinate while the vegetables are roasting.
After twenty minutes, carefully remove the sheet pan from the oven. Move the roasted vegetables to the sides to create space in the center for the chicken.
Place the marinated chicken breasts right in the middle of the pan and pour any remaining ranch dressing over them. This will keep the chicken moist and flavorful.
Return the sheet pan to the oven and continue to bake for twenty-five minutes, or until the chicken is fully cooked through and the juices run clear.
Once done, remove the baking sheet from the oven and allow the dish to rest for a few minutes. Serve hot, drizzled with the remaining ranch dressing for an extra creamy touch!