Preheat oven to 400 degrees F. Line jelly roll baking sheet with parchment paper or silpat mat. Set aside.
In a small bowl, whisk together cake flour, matcha powder, baking powder, and salt. Set aside.
In a large bowl, whisk together egg yolks, granulated sugar, and milk until pale in color.
In another clean bowl, whip egg white to medium-stiff peaks.
Add dry flour mixture to yolk mixture. Fold to combine. Add whipped eggs in three additions. Gently fold to incorporate egg whites.
Pour batter to prepared baking sheet. Use an offset spatula to spread batter into an even layer. Bake for 8-10 minutes until cake springs back to touch. Remove from oven and run a mini offset spatula around the edges of the pan to loosen cake.
Invert cake into a clean kitchen towel. Slowly and gently remove parchment (or silpat) from cake. Use the kitchen towel to roll cake into a log. Let the cake rest on a wire rack to cool to room temperature.
Once cake is cool, unroll the cake and remove the kitchen towel. Add a generous amount of strawberry mousse filing. Use an offset spatula to spread filling to an even layer.
Use your hands to gently roll the cake back into a log. Place the seam at the bottom of the cake to prevent it from unraveling. Cover log with plastic wrap and let chill in the fridge for at least 30 minutes to allow mousse to set up.
In a clean bowl, mix together strawberry puree and sugar. Adjust the amount of sugar depending on the sweetness of your strawberries. Take about 1/4 cup of strawberry mixture and place in separate bowl. You will use this for the gelatin.
Fill a small bowl of ice cold water to bloom gelatin for about 3 minutes. Squeeze out excess water from gelatin. Place soft gelatin sheets into bowl of reserved strawberry mixture. Microwave mixture 10 seconds at a time until gelatin has melted. Pour mixture into the rest of the strawberry puree. Set aside. Allow mixture to sit and come back to room temperature.
In another bowl, whip chilled heavy cream to medium peaks. Add whipped cream to cooled strawberry mixture in three additions. Gently fold cream into mixture.