Take it ever so easy on the rose water--it's meant to bring out the flavor of the sauce rather than stand out on its own. Add the rose water, then taste, then add more if you like. This is a perfect make-ahead dish, as it is best served chilled and will hold in the refrigerator for a week.
In a medium saucepan, combine the water and sugar and bring to a boil over medium high heat.
Stir in the cranberries and reduce to simmer, stirring occasionally and cooking until the cranberries pop and the mixture thickens a bit, about 20 minutes.
Remove from the heat, and add the rose water, pineapple, and drained mandarin oranges.
Cool to room temperature, then chill completely (at least a couple of hours).
Immediately before serving, stir in the nuts and garnish with more nuts on top.