Heat oven to 350°F. Line a 15 x 10-inch jelly roll pan with parchment paper, leaving an extra 1-inch of parchment sticking up on both 15-inch sides of the pan so that you can easily lift the cake out and roll it up after baking.
In a medium bowl, whisk together flour, cocoa powder, baking powder, and salt until evenly combined. Set aside.
In the bowl of a stand mixer, whisk eggs and granulated sugar for 1 minute until thick. Add the melted butter and vanilla extract, and whisk until just combined. With the mixer on low speed, add the flour mixture and mix until just combined.
Spread the batter evenly into prepared pan. Bake for 11 minutes, or until top of cake springs back when touched. Carefully lift the parchment paper and cake out onto a flat (and heat-safe) surface. Carefully and slowly (the cake will be very hot), use your hands to roll the cake starting at the short end, until it is completely rolled up. Transfer the cake roll to a wire rack, and cool until it reaches room temperature.
While the cake is cooling, make the cherry buttercream filling.
To make the Buttercream: Add the cherries, granulated sugar, and lemon juice to a medium saucepan and cook over medium heat until the mixture begins to boil and juices start to release. Continue cooking and stirring, smashing the cherries with a firm spoon as they soften ,until all the cherry juices have released, about 8-10 minutes.
Use a fine mesh strainer over a bowl to strain the cherries, using the back of a spoon to press as much cherry juice out as possible. You should get about 1/3 cup. Refrigerate cherry juice until completely cooled.
In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and salt together on high speed until smooth and creamy, about 2-3 minutes.
Add the powdered sugar 1 cup at a time, and mix on low until all powdered sugar has been added, then mix on high until creamy and combined. Add the cooled cherry juice and almond extract and mix on high until light and fluffy, about 2-3 minutes.
Once the cake has reached room temperature, transfer the cake roll to a flat surface, and carefully unroll it until it is flat again (the ends may stayed curled a bit - that's ok!) Spread a layer of cherry buttercream about 1/2" thick over the cake, leaving about a 1/2-inch border on all sides. Then carefully re-roll the cake, gently peeling away the parchment paper as you roll until you can completely remove and discard it. Tightly wrap the chocolate roll in plastic wrap and refrigerate at least one hour.
Remove and unwrap the chocolate roll and transfer it to your serving dish. Lightly dust with powdered sugar, top with additional cherry buttercream and fresh cherries, if desired*. Slice and serve!
If you have leftovers, just re-wrap the chocolate roll in plastic wrap and store in the refrigerator for up to 3 days.