Preheat the oven to 400°F. Slice the eggplant, mushroom, and onion. Transfer to a parchment-lined baking sheet and roast for 25 minutes, until eggplant is slightly golden.
After the vegetables are roasted, add them to the food processor along with the remaining ingredients. Blend the ingredients for 30 seconds at a time, making sure to scrape the sides so all the ingredients are evenly combined. Blend until you achieve a thick, uniform texture with no large chunks.
Scoop out a tablespoon or two of the mixture and using your hand, roll into a bite sized meatball. This recipe makes about 16-20 meatballs depending on the size.
Place the meatballs on the same baking pan, and roast for 15 minutes, gently flipping halfway through. They should develop a golden-brown crust on the outside
Serve with your favorite marina sauce. Enjoy!