1. Preheat your oven to 180°C (350°F). Line a baking tray with parchment paper.
2. Separate the egg whites and yolks into two bowls. Beat the egg whites until stiff peaks form.
3. In another bowl, whisk the egg yolks and sugar until pale and thick. Add the milk and vegetable oil, and mix well.
4. Sift the cake flour and matcha powder together, then fold into the egg yolk mixture.
5. Gently fold the beaten egg whites into the matcha batter in three additions.
6. Pour the batter into the prepared baking tray and spread evenly. Bake for 10-15 minutes, or until a toothpick inserted into the center comes out clean.
7. Let the cake cool slightly, then remove from the tray and peel off the parchment paper. Roll the cake with the parchment paper and let it cool completely.
8. For the filling, whip the heavy cream and sugar until stiff peaks form.
9. Unroll the cooled cake and spread the whipped cream evenly over the surface. Roll the cake back up without the parchment paper.
10. Chill the roll cake in the refrigerator for at least 1 hour before slicing and serving.