Preheat the oven to 350 and line an 11x17 inch rimmed baking sheet with parchment paper. Grease the paper and pan sides very well. Dust thoroughly with 1 tablespoon of the cocoa powder.
In a medium bowl, whisk together ¼ cup of the cocoa powder, the powdered sweetener, and the gelatin.
In another medium bowl, beat the egg yolks with the BochaSweet until lighter yellow and thickened, about 2 minutes. Beat in the coffee and the vanilla.
Using clean beaters and a large clean bowl, beat the egg whites with the cream of tartar and salt until they hold stiff peaks.
Gently fold the egg yolk mixture into the egg whites. Then fold in the cocoa powder mixture until no streaks remain. Spread the batter even in the prepared pan and bake 10 to 15 minutes, until the top springs back when touched.
Remove from the oven and let cool a few minutes, then run a knife around the edges to loosen. Sprinkle with the remaining 1 tablespoon of cocoa powder. Cover with another large piece of parchment paper, and then a kitchen towel. Place another large baking sheet overtop and flip the whole thing over. Keep covered and warm as you prepare the filling.
In a small bowl, beat the cream cheese with ¼ cup whipping cream until smooth.
In a large bowl, beat the remaining whipping cream with the sweetener and vanilla extract until it holds soft peaks. Then add the cream cheese mixture and continue to beat until stiff peaks form. Do not over-beat.
When ready to fill, uncover the cake and gently peel off the parchment from what is now the top of the cake. Spread the frosting evenly overtop, leaving a ½ inch border around all the edges.
Starting at one of the short ends, gently and carefully roll up the cake. The inner, tighter rolls may crack a little but this will be hidden in the inside of the cake. Place seam-side down on a cake platter.
Cut off about 3 or 4 inches of the end of the cake roll on the diagonal and place this piece up against the side of the main roll with the cut end exposed, to resemble a branching log.
Prepare the chocolate buttercream as directed. Spread the frosting over the tops and sides of the cake roll, leaving the cut ends exposed for visual interest. (feel free to cover the uncut end of the roll entirely with frosting).
Drag a fork in long lines all over the cake to rough up the frosting. Garnish with fresh rosemary twigs and a few fresh cranberries, if desired.