Remove the roasting chicken from the package. Pour the blood and juices from the bottom of the package onto a cookie sheet. Turn on the oven to 375 degrees Fahrenheit. Cook the blood and juices in the center of the oven until dried. Scrape off the dried material into a container, let it cool and put it in the refrigerator. Roast the chicken itself as you normally would.
Pull the bones from the roasted chicken and pick them clean. Lay the bones in a single layer on a cookie sheet. Place the cookie sheet on your kitchen counter for three or four days, until the bones are completely dried out.
Over several more days, put the cookie sheet in the oven after baking something else, while the oven is still hot but turned off. Repeat this until the bones are brittle enough to crush.
Put the bones into a food processor, put the lid on and use the "Pulse" setting to reduce the bones to a rough, pebbly mixture. Add the dried blood and Pulse until blended. Add the resulting blood and bone meal to your garden soil.