Here's an easy way to roast garlic in the oven without using tin foil, which will leach heavy metals (aluminum) into your food.
Preheat oven to 400 degrees F.
Drizzle olive oil over the head of garlic (skin on) in the center of a roasting pan or cast iron skillet. Roast for 20 minutes or until the garlic is tender on the inside.
Remove from the oven, set aside to cool for 2-3 minutes then peel and serve.