Preheat oven to 180°C. Grease 23cm square cake pan with butter; lightly sprinkle with flour.
Beat cake mix, oil, 275ml water and egg whites in large bowl with electric mixer on low speed until moistened. Beat on medium speed 2 minutes. Fold in ground almonds with large spoon, then pour into pan.
Bake 40 to 45 minutes or until toothpick inserted in center of cake comes out clean. Cool 10 minutes in pan; remove to cooling rack positioned over plate.
Heat sugar and 3 tablespoons water in small saucepan over medium heat, stirring occasionally, until sugar is dissolved. Heat to boiling; cook 2 minutes, then stir in rose water. Remove from heat.
Pierce cake all over with toothpick, then slowly pour over or brush with sugar syrup. Cool completely on rack.
Beat whipping cream mix and cold milk in medium bowl as directed on package. Spoon into decorating bag fitted with star tip.
Cut cake into squares; top each serving with a roasted almond. Top with whipped cream.