how long to cook a boston butt roast
1 Cover tightly. 2  Preheat oven to 425 degrees F for 15 minutes. 3  Place the roast in the oven and immediately reduce the temperature down to 200 degrees F. 4  Roast for about 4 hours or until the meat is falling-apart tender (cooking time will vary depending on the size of the roast). Place the roast in the oven and immediately reduce the temperature down to 200 degrees F. 2  Roast for about 4 hours or until the meat is falling-apart tender (cooking time will vary depending on the size of the roast).