Heat oven to 400°F. Spread bones, onions, and carrots in a single layer in a large roasting pan. Roast for about 1 hour or until the bones and vegetables are dark golden brown.

Transfer bones and vegetables to a large stock pot leaving fat and juices in the pan. Pour off all the fat then return the roasting pan to the stove top. Place over medium-high heat and add 1/2 cup wine and 1/2 cup water or just 1 cup of water. Scrape up any browned bits on the bottom of the pan with a wooden spoon then pour all the contents of the pan into the stock pot with the bones.

Add the bay leaves and peppercorns to the pot, then add 20 cups of water or enough to cover the bones completely. Bring to a boil.

Skim off any bubbly scum that floats to the top and reduce the heat to low. Cover and simmer at least 4 hours or up to 8. Strain stock into a large container then divvy up into smaller containers to freeze. Stock will keep for up to 3 months in the freezer or 1 week in the refrigerator.