Preheat the oven to 400°F/205°C.
Season the inside of the chicken with salt and pepper. Place the lemon halves, thyme and rosemary inside the chicken cavity. Truss the chicken with kitchen twine.
Smear 1 Tbsp. oil over the chicken and sprinkle with salt and pepper. Pour 1 Tbsp. oil into the bottom of a 7-qt. cast iron Dutch oven.
Transfer the chicken to the pan. Roast for 30 minutes, uncovered.
Reduce the heat to 350°F/180°C.
Add the vegetables to the pan and drizzle them with the remaining oil and sprinkle with salt and pepper.
Return all to the oven and continue to roast chicken, uncovered for 60 - 90 minutes or until it is thoroughly cooked and registers 165°F/74°C. (Cooking times will vary depending upon the size of the chicken.)
After roasting, allow the chicken to rest 10 minutes then slice, sprinkle with parsley and serve.