Put your frozen meatballs in the Crock-Pot.
Pour both jars of marinara sauce into the Crock-Pot over the meatballs.
Cover and cook on high for 4 hours. Note: my slow cooker cooked very fast so these were done in under 4 hours. The meatballs are done when the internal temp is 160°F.
Preheat the oven to 350°F. Place the rolls on a baking sheet, face up and open. This will toast the inside of the rolls.
Toast for about 5 minutes or until the insides start to get brown and crispy.
You can 2 slices of mozzarella cheese to the inside of the rolls and return the oven until the cheese melts. OR you can wait until the end to top your meatballs with the cheese so it melts over the top.
Add about meatballs to each roll until full but not over stuffed.
Garnish with Parmesan and parsley. Optional: serve with additional marinara from the Crock-Pot for dipping.