Combine the breadcrumbs and milk in a bowl and let them soak until fully absorbed.
Add the ground beef, ground pork, egg, grated Parmesan, minced garlic, salt, pepper, dried oregano, dried basil, and breadcrumb mixture, then mix gently until just combined.
Form the mixture into small meatballs without packing them tightly.
Heat olive oil in a skillet over medium heat and brown the meatballs until they develop a crust and hold their shape.
Add the meatballs to the sauce and simmer for 20 minutes.
Lightly toast the hoagie rolls to create structure.
Assemble the meatballs in the rolls, spooning sauce over them and adding shredded mozzarella.
Melt the cheese gently until just softened and cohesive.