Cut the strawberry roulade into pieces. Whip the cream.
Line a bowl generously with cling film.
Mix the strawberry yoghurt, sour cream and cream together.
Squeeze out the soaked gelatine and dissolve in hot rum, then stir quickly into the strawberry cream after cooling. If you want, you can add fresh, sliced strawberries and powdered sugar.
Cover the bowl with strawberry roulade very tightly, spread the whole cream over it, finally cover it with roulade again and wrap it with the protruding foil, weigh it down and put it in the fridge overnight.
Turn out and decorate with chocolate icing or powdered sugar.