See Georgia Johnson’s post on this.
My well-used Le Creuset signature risotto pot 6 3/4 QT / 6.2 L works well to roast the chicken and potatoes, details below. Buy a decent quality chicken if you can. The finished potatoes are nicely roasted and creamy.
Chicken
1 whole 5 to 6 lb chicken (Note 1)
Kosher salt and freshly ground pepper
1 teaspoon thyme leaves, optional
Potatoes
Yellow potatoes or Yukon gold
Kosher salt
Butter
Prep the chicken: At least one day/the night before, untie (and keep) the string keeping the chicken legs together. Rinse the chicken removing the kidneys and other organs from the cavity and pat dry. Place the chicken on a sheet pan. Sprinkle about 1 tbsp kosher salt, generously coating the chicken outside and in the cavity. Season to taste with pepper. Place the chicken uncovered in the fridge. Read more about this method, called dry brining.
Prep the potatoes: earlier in the day, bring a large pot of water to boil. Add 1 to 1.5 tablespoons of salt. Add potatoes and cook until almost done, about 8/10 minutes when a paring knife placed in a piece meets a little resistance. Pour into a colander, place back in the pot and set aside or put in a lidded container in the fridge.
Remove the chicken from the fridge an hour before you plan to cook it. Using the string that you saved, tie or wind legs together. You can also use butcher’s twine.
Preheat oven to 425°F, with a rack on the bottom position. Place the chicken in the center of the casserole dish and surround it with the partially cooked potatoes. After 30 minutes remove the pot, stir the potatoes to check they are not burning and return to the oven. Drop knobs of butter over the potatoes only. At 60 minutes, there should be some gravy. If not much, drop more knobs of butter over the potatoes and stir to check they are roasting somewhat evenly. Chicken should be roasted until it reaches an internal temperature of 165°F. Remove to a cutting board, tent loosely with tin foil or a silicon sheet and rest for 10 minutes. Carve and serve.
Note 1: I usually get a 2 to 3 lb chicken and cook for about 1 1/2 hours.