Preheat the oven to 400°F (200°C). Line a baking tray with parchment paper.
Divide the pizza dough into equal portions depending on how large you want the calzones.
Roll each portion into a ball, then roll each ball into a thin round crust on a lightly floured surface.
Spread a small amount of pizza sauce over one half of each dough round, leaving the edges clean.
Add cheese, salami, onion, olives, mushrooms, and any additional toppings onto the sauced half.
Fold the empty half of the dough over the filling to create a half-moon shape.
Press the edges firmly with your fingers to seal.
For extra sealing, fold the edge inward toward the filled side and press again.
Carefully transfer the calzones to the prepared baking tray.
Brush the tops lightly with olive oil if desired.
Bake for about 15 minutes or until the tops and bottoms are golden brown.
Let cool slightly before serving.