Preheat the oven to 450°F. Grease a 9×13-inch baking dish with non-stick cooking spray or oil. Set aside.
Combine all ingredients except the marinara sauce in a large mixing bowl and mix by hand until thoroughly incorporated.
Roll the mixture into round, golf ball-size meatballs (about 1 1/2 inches), making sure to pack the meat firmly. Place the balls in the prepared baking dish, lining them up snugly and in even rows vertically and horizontally to form a grid. The meatballs should be touching one another.
Roast for 20 minutes, or until the meatballs are firm and cooked through. The internal temperature of the meatballs should be 165°F.
While the meatballs are roasting, heat the marinara sauce in a small saucepan over medium-high heat, stirring often.
When the meatballs are firm and fully cooked, remove them from the oven and drain the excess grease from the pan. Pour the marinara sauce over them. Return the meatballs to the oven and continue roasting for another 15 minutes.
Adapted from Epicurious.