Preheat the oven to 400 degrees F. To roast the garlic—peel the loose skin off of the garlic bulb and cut off the tip of the garlic cloves while they are still in the bulb.
Brush the bulb with a little bit of olive oil and wrap it in aluminum foil. Place the wrapped garlic onto a baking sheet and bake for 30-35 minutes. Remove the garlic from the oven and allow it to cool.
Grease a casserole dish with aluminum foil. Heat the oven to 350 degrees F. In a large bowl combine ground beef, ground pork, egg, breadcrumbs, minced onion, minced rosemary, Worcestershire sauce, salt, and pepper.
Peel the roasted garlic and take out the cloves. Add them to the bowl with the other meatball ingredients. Mix until all of the ingredients are fully incorporated. Roll the mixture into 1.5-inch meatballs and place them into the casserole dish.
Place individual raw garlic cloves between the meatballs and rosemary sprigs on top. Cover the baking dish with aluminum foil and bake for 35 minutes.
Take off the foil and bake for another 10-15 minutes or until fully cooked (the internal temperature has reached 160 degrees F.).