Meringue Roulade with Rose Petals and Fresh Raspberries

Name: Meringue Roulade with Rose Petals and Fresh Raspberries
Ingredients: 4 large egg whites; 1 1/4 cups/250 g superfine sugar; 1 teaspoon vanilla extract; 1 teaspoon white wine vinegar; 1 teaspoon cornstarch; 3 1/2 ounces/100 g mascarpone; 1 tablespoon confectioners' sugar; 1 1/2 tablespoons rose water; 1 3/4 cups/400 ml heavy cream; 1 1/4 cups/150 g fresh raspberries; 2 tablespoons dried rose petals; 1 teaspoon slivered pistachios (or regular, if unavailable, crushed); Confectioner's sugar, for dusting