Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Dice the sweet potato into small half-inch cubes, slice the zucchini into rounds, and chop the red bell pepper into bite-sized pieces.
In a small bowl, whisk together the olive oil, lemon juice, minced fresh rosemary, garlic powder, sea salt, and black pepper to create the marinade.
Place the chicken breast on one side of the baking sheet and spread the prepared vegetables across the remaining space.
Drizzle the lemon-herb marinade over the chicken and vegetables, using your hands or a brush to ensure everything is evenly coated.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are fork-tender.
Let the chicken rest for 5 minutes before slicing to keep it moist, then serve alongside the roasted vegetables.