Strain the ricotta by wrapping it in paper towels and placing it in a bowl.
Let the ricotta strain for 30 to 40 minutes, changing the paper towels every 10 minutes.
In a mixing bowl, combine the graham cracker crumbs, ground cinnamon, cocoa powder, and granulated sugar.
Stir until the dry ingredients are evenly combined.
Add the melted salted butter to the crumb mixture.
Mix thoroughly until the crumbs are evenly coated and the mixture holds together when pressed.
Press the crumb mixture firmly into the bottom and sides of a tart pan.
Ensure the crust is pressed well into the grooves of the pan.
Place the crust in the freezer to chill while preparing the filling.
In a large mixing bowl, beat the softened cream cheese until smooth.
Add the strained ricotta to the cream cheese.
Mix until smooth and creamy.
Add the sifted powdered sugar.
Mix until fully incorporated and the filling is smooth.
Gently fold in the finely chopped dark chocolate.
Add the orange zest.
Fold gently until the chocolate and orange zest are evenly distributed throughout the filling.
Remove the chilled crust from the freezer.
Spread the cannoli filling evenly into the prepared crust.
Smooth the top with a spatula.
Cover the pie with plastic wrap.
Refrigerate for at least 3 hours, or overnight, until the filling is firm and set.
Just before serving, sprinkle the top with chopped roasted pistachios.
Dust lightly with powdered sugar.
Slice and serve chilled.