Preheat oven to 425 degrees.
Make spaghetti as desired, or reheat leftover spaghetti (sauce and noodles mixed together).
Place the 4 Hoagie Roll halves onto a baking sheet lined with foil. Spread each piece with 1 tablespoon butter. Sprinkle 1 teaspoon of garlic powder onto each piece.
Bake in oven for 5 minutes or until golden brown. You may broil it as well if you’d like. Remove from oven.
Top each piece of bread with about 1 cup of spaghetti. Then sprinkle on 1/2 cup of mozzarella cheese. Bake for additional 5 minutes or until cheese is nice and bubbly.
Allow to cool and enjoy!