Soak gelatine in cold water. Wash and clean the strawberries and puree half of them finely with a hand blender.
For the mousse, mix yoghurt, sour cream, icing sugar, vanilla sugar and half of the lemon juice in a bowl. Heat the rest of the lemon juice in a small pot. Squeeze out the gelatine and dissolve in it. First stir 2-3 tablespoons of yoghurt cream into the gelatine, then stir everything into the remaining yoghurt cream. Chill for about 10 minutes until the mixture begins to gel. Whip the cream until stiff and fold into the yoghurt cream.
Layer the strawberry puree and yoghurt mousse alternately in ten glasses (approx. 200 ml each). Finish with strawberry puree. Cover and chill for about 1 hour.
For the roses, thaw the puff pastry side by side on a floured work surface. Cut into about 20 strips (2-3 cm each). Cut the remaining strawberries into thin slices and place them on the strips. Carefully roll up the strips and at the end slightly
Place the roses on a baking tray lined with baking paper. Bake in a preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer) for approx. 15 minutes. Let them cool down. Serve with mousse.