Adjust the oven rack to the lowest position and place a pizza stone or a couple cast-iron skillets turned upside down on the oven rack. Preheat the oven to 500 °F (260°C) for at least 30 minutes. Line a baking sheet with parchment paper and lightly slick it with oil. Turn the risen dough out onto an unfloured work surface. Divide the dough in half, and then cut each half into thirds. Gently shape each piece of dough into a ball. Move to the baking sheet and cover with plastic wrap that you've slicked with a little oil. Let the dough rest for at least 15 minutes but no more than 30 minutes.
Cut eight 9-inch squares of parchment paper. Working with 1 piece of dough at a time and keeping the other pieces covered, roll the dough into a 9-inch round. Place the dough round on a parchment square and cover it with another parchment square. Roll out another dough ball, set it on top of the first dough round, and cover it with a parchment square. Repeat to form a stack of 3 dough rounds, covering the top round with a parchment square. Form a second stack of 3 rounds with the remaining dough balls and parchment squares.
Remove the top parchment square from the first stack of dough rounds and place it on the work surface. (If the dough rounds have shrunk, gently roll them out again to 9-inch rounds.) Spread 1/6th of the ricotta mixture on the bottom half of each dough round, leaving a 1 inch border plain. Place 1/6 of the sausage mixture on the cheese filling.
Fold the top half of the dough over the filling-covered bottom half, leaving 1/2 inch border uncovered. Gently place your fingertips on the top layer of dough and press ever so slightly to let any air escape. Beginning at one end of the seam, place your index finger diagonally across the edge and use your thumb to gently pull the bottom layer of the dough over the tip of your index finger, and press the dough to seal. Repeat the process until the calzone is fully sealed. With a very sharp paring knife or razor blade, cut 5 slits, each about 1 1/2 inches long, diagonally across the top of the calzone, making sure to cut through just the top layer of dough and not completely through the calzone.
With a pastry brush or your fingertips, brush the tops and sides of the calzones with oil and lightly sprinkle with kosher salt. Trim the excess parchment paper. Slide the calzones and their parchment onto a pizza peel or an upside-down baking sheet and then slide them onto the hot pizza stone or the bottom of the cast-iron skillets. (You'll probably need to bake the calzones in batches. Typically 2 will fit on a baking stone.) Bake until the calzones are golden brown, about 15 minutes. Carefully slide the parchment and calzones onto the pizza peel or upside-down baking sheet and transfer to a wire rack. Remove the calzones from the parchment and, if you can resist diving straight in, let them cool for 5 minutes.