Place the carrots, potatoes, and onion in a large bowl. Drizzle with 3 tablespoons of olive oil, then season generously with salt and pepper. Toss it all around well to coat, then place in a large cast-iron skillet. You may also use a large baking dish instead, like a 9x13 pan.

Dry the chicken very well with a paper towel, then season the inside and outside of the chicken with salt and pepper. Place the garlic, rosemary, and lemon wedge into the cavity, then truss the chicken with kitchen twine.

Place the chicken on top of the bed of vegetables, then roast for 25 minutes. Turn the oven down to 400ºF, and brush the outside of the chicken all over with olive oil. Continue cooking the chicken for approximately 45 more minutes, until the chicken registers 160ºF with a thermometer, reading where the thigh meets the breast. Or, you can check that the juices run clear at this spot. The chicken may need an additional 5 or 10 minutes of cooking time, depending on the size of the chicken.

Once the chicken has finished cooking, let it rest at room temperature for at least 15 minutes for the juices to redistribute. Now it’s ready to serve!