I am not a cake expert by any means but if you are looking for a cream frosting recipe to finish off the cake prior to adding the sugar roses you can try this. Keep in mind that since this is not made with any additives you may have to make the cake, refrigerate it and eat it quickly else I am not sure what would happen to the texture of the cream frosting.
Purchase rose extract (I know it's available at Indian stores and I am sure also at middleeastern store). I like the oil based extracts over rose water since they are more potent in flavor. I use rose extracts a lot in dishes I make so I know they are readily available.
Use 1 tsp of extract for 1.5 cups of cream for a subtle yet distinct flavor. Also add a pinch of red food color to the cream to give it a pink hue. Beat it all together until the cream is stiff.
Use this to frost the cake. I am sure you can make a butter and sugar shortening using this oil as well.