Preheat your oven and cast iron skillet, placed on the lower rack of your oven, to 500 degrees F (260 degrees C).
While preheating, remove any excess fat from your chicken and place the gizzards, liver, heart aside. Trim the tail off, tuck the wings under the back, and tie up the back legs (if desired). *Also, I like to place half of my lemon in the body cavity of the chicken, so don't forget to do this first if you are going to tie the legs!
Use the olive oil to rub the chicken skin all over the roasting surfaces, breast side up, then season generously with salt, pepper, and thyme.
Place the chicken carefully into the center of your heated cast iron skillet with the breast facing upward and roast at high heat for 15 minutes. Then set the temperature to 350 degrees F (175 degrees C) and finish roasting for an additional 40 minutes, or until an inserted meat thermometer reads 160 degrees F (71 degrees C) in the meatier portions of the chicken (breast and thigh).
Remove from the oven, squeeze the juice from one half of the lemon (assuming that you have placed the first half within the chicken cavity) over the roasted surfaces of the chicken. Tip the chicken to allow the body cavity to drain and the lemon to roll out.
Allow your stunning cast iron roasted lemon herb chicken to rest for approximately 10 minutes before carving and serving.