In a small bowl, thoroughly combine all the spices. Remove giblets from chicken, clean the cavity well and pat dry with paper towels.
Rub the spice mixture into the chicken, both inside and out, making sure it is evenly distributed and down deep into the skin. Place in zipper food storage bag, seal and refrigerate overnight or freeze.
When ready to roast chicken, stuff cavity with onions, and place in a shallow baking pan. Roast uncovered at 250 degrees for 5 hours.
After the first hour, baste chicken every 30 minutes with pan juices. The pan juices will start to caramelize on the bottom of the pan and the chicken will turn golden brown.
Let chicken rest 10 minutes before carving.