About an hour before you are ready to start, separate the cold eggs and put the whites in the bowl of a stand mixer. Put the yolks in a second large mixing bowl. Allow them to come to room temperature.
Preheat the oven to 375 degrees F. Spray an 11-by-17-inch rimmed baking sheet with cooking spray; line the bottom with parchment paper and spray the parchment.
Put the flour, cocoa powder, baking powder and salt in a medium size bowl and whisk for about 2 minutes. Set aside.
With the whisk attachment, beat the egg whites and cream of tartar on medium speed until soft peaks form. Gradually beat in 1/4 cup granulated sugar. Increase the speed to medium high; beat until stiff peaks form.
Meanwhile, whisk the egg yolks with the remaining 1/2 cup granulated sugar, the oil, milk, vanilla and espresso powder. Add the flour mixture to the egg mixture and stir until well blended.
With a heavy duty scraper, stir one-third of the egg whites into the batter, then gently fold in the remaining whites in two batches. Spread the batter in the prepared pan; bake until the cake springs back when gently pressed, 10 to 12 minutes. Let cool 5 minutes.
Sift reserved 2 tablespoons cocoa powder over the top of the warm cake and loosen the edges with a knife; lay a clean kitchen towel (not terry cloth) over the cake. Place another baking sheet over the towel and flip the cake with the baking sheets to invert it onto the towel. Remove the top baking sheet and parchment, then dust the cake with cocoa powder. Starting at a short end, roll up the cake and the towel together into a spiral. Transfer seam-side down to a rack and let cool completely.
Meanwhile, make the filling: Beat the butter and salt in a large bowl with a mixer on medium speed until creamy, 2 minutes. Add marshmallow cream and the vanilla; increase the speed to medium high and beat until fluffy, 2 minutes. Reduce the speed to low. Beat in the confectioners' sugar, then the milk, then increase the speed to medium and beat until thick and spreadable.
Gently unroll the cake. Spread the filling over the cake about 1/4 inch from the edges; reroll (without the towel). Trim the ends with a serrated knife, then transfer to a rack set on a baking sheet.
Make the glaze: Microwave the chocolate with the heavy cream in a microwave-safe bowl, stirring every 30 seconds, until smooth. Pour over the cake; spread to coat. Transfer to a platter and refrigerate 15 minutes.