I would suggest not roasting a chicken at such a low heat for so long. Here is a response to a similar question on another cooking forum:
A few days ago I printed out a recipe
from peacefulnightdove "BEST
Slow-Roasted Chicken". It sounded
wonderful but was to be roasted at 250 F (126 C)
degrees for 5 hours. That sounded like
a low temperature to me, so I emailed
the County Nutritionist and Health
Agent where I lived. Here is her
reply: Good for you JoAnn to be
suspicious! That is definitely outside
the USDA guidelines, and yes bacteria
may well be growing for quite a while
in there. Poultry especially should
not be done at less than 325 degrees.
You could use the same spices and
onions, increase the temp to 325 and
decrease the time. Figure about 20 min
per pound for the time. The safest way
is to use a meat thermometer, final
temp in the thigh should be 180
degrees.
http://community.tasteofhome.com/forums/t/173823.aspx
I would also suggest using a crockpot.
Roasting the bones will give you a darker brown stock than using the raw bones. To roast the bones, just stick them in an oven on high heat, around 450 for about 45 minutes, or until they are a nice golden caramelized color. Though you will want to make sure to keep an eye on them the first time, I'd check every 5 minutes after half an hour. Roasting the veggies with the bones will also add a slightly sweeter roasted flavor. It's like the difference of putting slices of raw onions on a burger compared to caramelized onions. You get a slightly sweeter, richer roasted flavor. Though it does turn down some of the other flavor notes, it's up to you which you'd rather have. Without roasting, you'd have a clearer "white" stock.
If you are using the butter as a base to roast the bones, I would set it aside and go with a higher smoke point oil like a peanut or corn oil. The low smoke point of the butter could leave a bitter, slightly burned flavor, especially with the longer roasting times.
I would leave the seasoning for the stock. Most spices will burn at a lower temperature, and salting the bones before you make your stock, could make your stock overly salty. It's easier to add more toward the end, than try to figure out what to do with salty stock.
I hope that helps!
Best Answer
That's the largest chicken I've ever heard of.
That said, 3 to 3.5 hours at 325℉ should be sufficient. Unfortunately time doesn't really matter when cooking chicken, but temperature. You should definitely be using a meat thermometer and cooking long enough for the breasts to reach 160℉ and the thighs 170℉.
If you don't have a thermometer the next best thing would be to poke the thigh when you think it's done and confirm that the juices run clear. If they are not clear, then it needs to be cooked longer.