Preheat your oven to 400°F (200°C). Rub the whole chicken generously with salt, pepper, cinnamon, and thyme, ensuring all sides are seasoned evenly.
Place the seasoned chicken on the center of a large sheet pan. Drizzle the chicken with a tablespoon of olive oil and massage it into the skin for even browning.
Scatter the cubed sweet potatoes around the chicken, then drizzle them with the remaining two tablespoons of olive oil. Toss gently to coat all pieces evenly with oil and spices.
Transfer the sheet pan to the oven and roast for about 45 minutes, or until the chicken skin is golden and crispy, and the sweet potatoes are tender and caramelized. Baste the chicken with juices from the pan halfway through if desired.
Remove the sheet pan from the oven and rest the chicken for 10 minutes before carving. The sweet potatoes should be soft with slightly crispy edges, while the chicken skin is crispy and aromatic.
Carve the chicken and serve alongside the roasted sweet potatoes, garnished with fresh thyme if desired. Enjoy the crispy skin contrasted with tender, flavorful meat and caramelized vegetables.