Preheat the oven to 400°F (200°C).
In a mixing bowl, combine the ground sausage, breadcrumbs, grated Parmesan cheese, milk, egg, minced garlic, oregano, basil, salt, black pepper, and red pepper flakes (if using). Mix until just combined; do not overmix.
Using your hands, form the mixture into approximately 1-inch meatballs and place them on a baking sheet lined with parchment paper or aluminum foil.
Make sure to space the meatballs about 1 inch apart to allow for even cooking.
Bake in the preheated oven for 20-25 minutes, or until the meatballs are cooked through (internal temperature should reach 160°F or 70°C) and have a nice golden brown color.
Once done, remove the meatballs from the oven and let them rest for a few minutes.
Garnish with chopped fresh parsley before serving.