While the vegetables roast, mix the remaining 1 tablespoon olive oil with the remaining 1 ½ tablespoons blackened seasoning. Rub the mixture evenly over both sides of the chicken breasts.
Remove the pan from the oven. Push the vegetables to the sides and nestle the chicken in the center.
Return the pan to the oven and bake for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with lightly charred edges.
Remove from the oven and let rest for 5 minutes. Garnish with chopped parsley if desired and serve.