Preheat the oven to 400 degrees.
In a mixing bowl, knead together all of the ingredients or the meatballs until well combined.
Form the meat mixture into 30 evenly shaped meatballs, and place into a 9x13 baking dish.
Bake for 30 minutes.
While the meatballs are baking, heat the marinara sauce over medium low in a pot.
Add in the spinach, and cook until it is wilted. Set aside.
Remove the meatballs from the oven, and drain excess grease.
Spoon the sauce mixture over the meatballs.
Drop the ricotta over the mixture by the teaspoonful.
Sprinkle with the mozzarella cheese and bake for another 30 minutes.
Let rest for 10 minutes before serving.