Add olive oil to a large cast iron skillet or to a roasting pan, and heat over medium-high heat. If using a roasting pan, you may need to use it over two burners.
Sprinkle desired amount of salt and pepper over chicken breasts. Then place the chicken breast sides down in the pan. Add the cubed sweet potatoes, and cook in pan/skillet for 4-5 minutes or until the chicken is browned.
Turn the chicken over and pour lemon, rosemary, and garlic over the chicken and potatoes. Top with sliced lemons.
Bake at 400 degrees for 30-35 minutes, or until the chicken is done. This varies for each oven.