Make the sauce: In a large saucepan over medium heat, saute the garlic and red pepper flakes in the oil 1 minute, stirring. (Do not brown the garlic.) Stir in the tomatoes and salt. Bring the sauce to a boil, reduce the heat to low and simmer, stirring occasionally, 15 minutes.
Meanwhile, make the meatballs: Preheat the oven to 450 degrees F. In a large bowl, mix the beef, sausage, onion, garlic, thyme, parsley, egg, parmesan, breadcrumbs, ricotta and salt with your hands. Form 1 1/2-inch balls out of the meat mixture. Heat a large ovenproof skillet (preferably cast iron) with a bit of olive oil. Working in batches, add the meatballs and brown on all sides, about 4 minutes. Return all the meatballs to the skillet and place in the oven to finish cooking, 10 minutes.
Toss the meatballs with 3 cups of the prepared sauce. Place on the toasted slider buns and sprinkle with parmesan and parsley.
Photograph by Jennifer Causey
Recipe adapted from Catelli's by Guy Fieri for Food Network Magazine