Preheat your oven to 350°F (175°C).
In a bowl, mix together melted butter and granulated sugar until well combined.
Add the eggs and vanilla extract to the butter-sugar mixture; whisk until smooth.
Sift in cocoa powder, flour, and salt; mix until just combined.
Roll out the pie crust on a floured surface and cut it into squares.
Spoon the brownie batter into the center of each pie crust square.
Fold the edges of the pie crust over the brownie filling, sealing them tightly.
Place the assembled rolls on a baking sheet lined with parchment paper.
Bake in the preheated oven for 20-25 minutes, or until the crust is golden brown.
Let the rolls cool slightly before dusting with powdered sugar and serving.