Bring a large pot of heavily salted water to a boil over medium-high heat. Meanwhile, arrange a rack in the middle of the oven and heat the oven to 425°F. Finely chop 1 small yellow onion (about ¾ cup) and 2 garlic cloves. Coarsely chop ¼ cup fresh parsley leaves, then chop some more for garnish if desired.

Whisk 2 large eggs in a large bowl until combined. Add 2 ½ pounds ground beef, 2 ounces grated Parmesan cheese (about ½ cup), ½ cup dried panko breadcrumbs, 1 tablespoon kosher salt, onion, garlic, and parsley to the bowl and mix with your hands until combined, making sure not to overmix.

Form the mixture into 1-inch wide meatballs (about 2 tablespoons each). Place the meatballs in a single layer on a rimmed baking sheet.

Roast until browned and cooked through, 8 to 10 minutes. Meanwhile, add 1 pound dry spaghetti to the boiling water and cook until al dente according to package directions, 9 to 11 minutes. Drain the pasta, then return to the now-empty pot. Add ½ (24-ounce) jar Prego® Traditional Italian Sauce and toss to coat.

Add the remaining 1 ½ jars Prego® Traditional Italian Sauce to a large, high-sided skillet or Dutch oven and bring to a simmer over medium-high heat. Add the meatballs and spoon the sauce over the meatballs to coat. Transfer 20 meatballs and ¾ cup sauce into a single airtight container and refrigerate for the Rollover Dinner.

Transfer the spaghetti to shallow serving bowls and top with meatballs and sauce. Serve garnished with more Parmesan cheese and chopped fresh parsley.