Place meatballs and sauce into a medium saucepan over medium heat. Cover and bring to a simmer. Simmer for 20 minutes or until the meatballs are heated through, stirring often.
Turn rolls on their sides, sliced side up. If they aren't pre-sliced cut them about 3/4ths of the way through but not all the way.
Divide meatballs and sauce between the rolls, gently pushing the meatballs down.
Sprinkle cheeses over top along with the oregano.
Bake for 10-15 minutes or until the cheese is melted and the buns have started to brown.