Preheat your oven to 400 degrees Fahrenheit.
Set the chicken on the cutting board, breast side down. Using kitchen shears, cut along both sides of the backbone and remove it. Flip the chicken over and press down on the breast to flatten it out a little. (You may also ask your butcher to do this for you).
Lay the chopped sweet potatoes in the pan and season with salt and pepper. Rub 1 teaspoon salt all over the chicken, including under the skin, and set it breast side up, in an 8 x 11 baking dish or roasting pan. Sprinkle it generously with black pepper. Then rub olive oil on top of the chicken. Sprinkle the skin with fresh thyme and rosemary
Roast the chicken and stir the sweet potatoes after 30 minutes to ensure even cooking. Cook until an instant read thermometer inserted in the deepest part of the thigh registers at 170 to 175, about 50 minutes. Keep an eye on the pan juices, if they seem to be burning add a couple of tablespoons of water to the pan.
Let the chicken rest for a few minutes. Then cut into pieces, drizzle it generously with the pan juices and serve.
Tip: To save time ask your butcher to butterfly the chicken