Preheat the oven to 230 degrees C (fan 210 degrees C).
While the dough is resting, prepare the filling. In a large skillet over medium high heat, heat the olive oil.
Add the sausages and mushrooms and cook, stirring, until sausages are cooked through, 5 to 6 minutes.
Add the pizza sauce, and stir until evenly combined. Remove from heat.
Divide the dough into 4 equal-sized portions, and shape into rounds.
Working with one piece of dough at a time, roll the dough into a 6-inch disc.
Using a pastry brush, glaze the top edge of the disc with water.
Spoon 1/4 of the filling onto the lower half of the disc.
Top the filling with 1/4 of the mozzarella.
Fold the top half of the disc down over the filling, leaving a 1/2 border at the bottom.
Lightly brush some water over the edge of the top piece.
Fold the bottom edge over the top piece, and pinch to seal tightly.
Using a sharp knife, cut a 1/2-inch vent in the top of the calzone. Repeat for the remaining dough and filling.
Brush the tops with butter.
Sprinkle 1 teaspoon of parmesan on each calzone.
Place the calzones in a preheated baking sheet lined with baking paper and bake, until the filling is hot and the crust is golden brown, 15 to 20 minutes.