Heat a medium dutch oven over medium-high heat. Add the olive oil. Once lightly shimmering, add the garlic clove and sizzle for 30 seconds. Add the red pepper flakes and oregano. Carefully pour in the crushed tomatoes (it will immediately boil). Stir and season with sugar, if needed (i.e. if tomatoes are acidic) and salt and pepper.
Bring to a boil. Partially cover pot with lid and allow to gently simmer as you make the meatballs (about 20 minutes).
In a large mixing bowl, add all the ingredients for the meatballs, except the oil. Gently stir together, mixing only until everything is combined. If time allows, chill this mixture in the freezer for 10-15 minutes.
Using a small (#60) cookie scoop, scoop out some of the mixture. Using wet hands, quickly roll into a meatball. Keeping hands wet will prevent the mixture from sticking and make smoother meatballs. Repeat until all meatballs are formed. (A quick chill in the freezer helps them retain their shape as you cook them, if time allows.)
Heat a large skillet over medium heat. Add the olive oil. Once hot, add the meatballs in a single layer. Cook, browning on all sides. Remove from pan and repeat until all meatballs are browned.
Add meatballs to simmering pot of marinara. Gently stir and bring back to a gentle simmer. Cover and cook for 15 minutes.
To serve on rolls, preheat oven to 350°F (180°C). Place rolls on a sheet pan. Add 4-5 meatballs on each roll, top with a few spoonfuls of sauce and some mozzarella cheese. Bake for 5-7 minutes or until cheese is melted.
To serve with pasta, cook pasta according to package instructions. Toss with marinara sauce and meatballs. Serve immediately.