Take loose skin off the garlic bulb and cut off the tip of the garlic cloves, still in the bulb. Rub garlic bulb with a little bit of olive oil and wrap it in aluminum foil.
Preheat oven to 400°, place wrapped garlic on a baking sheet and bake for 40-45 minutes, depending on the size of garlic bulb. (Note: this step can be made the day before and you can just refrigerate roasted garlic in an air-tight food storage container until ready to use.)
Meatballs:
Preheat oven to 350° and spread some olive oil in a casserole dish that's big enough to hold these meatballs comfortably.
In a large mixing bowl, combine ground beef, ground pork, egg, bread crumbs, minced onion, minced rosemary, Worcestershire sauce, salt, and pepper. Carefully peel roasted garlic and take out the roasted garlic cloves. Add them to the bowl. Mix very well, until all ingredients are completely incorporated.
Roll about 1.5 inch meatballs and place them snugly in the casserole dish.
Stick individual, raw garlic cloves in between meatballs and add rosemary springs on top.
Bake the meatballs for about 30-35 minutes. (Exact time will depend on how large the meatballs are. You can cut into one to check for doneness.)