Preheat oven to 400F /200C / gas 6 and line a sheet pan with parchment paper.
Place the sweet potato in the middle of the sheet pan and pour on 1 tablespoon of the oil. Mix untilcoated and then cook for 15 minutes.
In a large bowl, combine diced chicken, peppers, onion, tomatoes, remaining oil, ranch seasoning, paprika, Italian seasoning and garlic salt.
Add the chicken mixture to the sheet pan, placing around the sweet potato.
Return sheet pan to the oven and cook for an additional 15 -18 minutes until the chicken is cooked through and the internal temperature is at least 165F / 74C.