Heat the oven to 500 degrees. In a medium-sized bowl, combine the ricotta, garlic, salt, oregano, red pepper flakes and parmesan. Taste and adjust the seasoning. Set aside.
On a floured surface, roll out an 8-inch circle. Smear a hearty layer of ricotta evenly across the dough, leaving a half inch border around the perimeter of the pizza. Top one-half of the dough with a handful of turkey, pepperoni, onions and mozzarella.
Gently fold the other half of the dough over the filling. Securely seal the calzone with a fork, making small ridges along the seam. Brush the top of the calzone with olive oil and sprinkle with kosher salt.
Place in the oven and bake, for 15 to 20 minutes, or until the dough is golden brown. Halfway through baking, open the oven and make a small slit in the top of the rising dough.
Remove from the oven and let cool for 5 to 10 minutes. Serve warm with red sauce for dipping.