In a skillet, brown sausage over medium high heat. Use a spatula to crumble meat while cooking. Drain on paper towel.
Add onions, bell peppers and mushrooms to same skillet. Season with salt and pepper and cook until vegetables are tender. Remove from heat and drain on paper towel.
In a small bowl, mix ricotta, Parmesan and 2 tsp of Italian seasoning. Set aside.
Divide pizza dough into 4 equal parts. Roll each piece into a 9 inch circle.
Leaving 1 inch border, spread 1/4 of ricotta mixture on half of circle. Top with sausage, vegetable mixture, mozzarella cheese, 5 pepperoni slices, a little more cheese and a few sprinkles of fresh basil. Fold the pizza dough over the filling, sealing the edges. Repeat until 4 calzones are made.
Cut 3 small vents in the top of each calzone and brush with melted butter. Sprinkle Italian seasoning on top.
Place each calzone on a large baking sheet, lined with parchment paper. Bake in preheated oven for 13 - 15 minutes. Serve warm with pizza sauce for dipping.
Notes
This recipe is versatile, so feel free to use whatever toppings you like to fill calzone.