Arrange a rack in lower third of oven with no racks above it; preheat oven to 425 degrees F. Place potatoes, carrots, thyme and rosemary in a 12-inch cast iron or other oven-safe deep skillet. Season with salt and pepper and pour in 1 cup of stock. Rub skin of chicken with olive oil, then season with salt and pepper. Place chicken breast-side-up on top of vegetables.
Roast chicken, basting with the pan juices every 20 minutes, about 60 to 75 minutes or until internal temperature reaches 165 degrees F. Transfer chicken to a platter, draining juices from the cavity of the chicken into the pan. Using a slotted spoon, remove vegetables and arrange around chicken on the serving platter.
Bring pan drippings to a simmer over medium heat. Add flour and whisk constantly for 1 minute. Add 1 cup of stock and whisk until smooth. Simmer until thickened, about 2 minutes. If too thick, whisk in additional stock 2 Tbsp. at a time until desired consistency is reached. Add cream, if desired, and season with salt and pepper to taste. Carve the chicken and serve with the vegetables and gravy.