Preheat your oven to 350°F an line a cookie sheet with aluminum foil.
In a large saucepan over medium heat, combine the meatballs and 3 cups of marinara sauce. Note: If i have large meatballs, I just do one per sandwich, but if the are smaller meatballs, then I use two per sandwich.
Simmer for 10-15 minutes, stirring occasionally, until the meatballs are heated through and the saucy is bubbling.
Without separating the rolls, slice the entire block of Hawaiian rolls horizontally to create a top and bottom layer.
Place the bottom layer in the foil lined baking sheet, and scoop 1-2 meatballs on each bun on the bottom layer. Top meatballs with freshly shredded mozzarella cheese. I do approx 1T per roll. Note: I prefer freshly shredded cheese. Pre-shredded cheese in the grocery store, has an anti-clumping agent added to it to prevent it from sticking together. Unfortunately, it also prevents if from melting well. My favorite tool is this attachment for my stand mixer that grates a whole block in seconds.
On the underside of the the top half of the rolls, spoon approx 1- 1 1/2 cups of marinara sauce (depending on how saucy you like them), and spread it evenly. Place the top layer of rolls over the cheese.
In a small bowl, melt 2T of butter and stir in 1/2t of Italian seasoning. Brush the seasoned butter over the tops of the rolls.
Bake at 350°F for 10-15 minutes or until the tops are golden brown and the cheese is melted. TIP: Keep a close eye on the rolls and if the tops start to get too crispy, cover them with tin foil to protect them from burning.
Allow the sliders to cool for a few minutes before slicing along the roll seams. Serve warm. If I have extra marinara sauce, left in the sauce pan, I scoop it into small bowls for dipping.