Heat a grill for medium indirect heat.
Combine the beef and sausage in a large mixing bowl. Season with kosher salt and black pepper. Add the breadcrumbs, milk, egg, Parmesan, garlic, and parsley. Use clean hands to gently work the meat mixture together. Try not to over mix.
Divide the meatball mixture into 12 meatballs, packing them loosely into rounds. Arrange the meatballs in a baking dish and season with more salt and drizzle with olive oil. Cook the meatballs for 20 minutes at medium heat.
While the meatballs cook, make the red sauce. Combine the canned tomatoes, garlic, Salt Pepper + Three Chiles, basil and olive oil in a large bowl. Use an immersion blender to puree the sauce until smooth.
When the meatballs are browned and almost cooked through, pour about 2 cups of the sauce over the meatballs and cook until bubbly, about 15 minutes more. Remove the meatballs from the grill to rest.
Brush the La Brea Bakery Take and Bake Ciabatta Rolls with avocado oil and grill for 1 to 2 minutes over direct heat, until charred.
Build the sandwiches by smearing pesto on each half of the La Brea Bakery Take and Bake Ciabatta Rolls, top the bottom half with 3 meatballs, lots of grated Parmesan.