In a saucepan, stir together water and sugar. Bring to a boil over medium-high heat, then simmer for 1 minute or until the sugar is completely dissolved and the mixture is slightly thickened. Cool for 15 minutes.
In the bowl of a food processor or blender, add strawberries, lemon juice, orange juice, champagne and cooled simple syrup. Blend until completely smooth.
Once ice crystals have formed around the edge of the pan, whisk the mixture to distribute the crystals. Return the pan to the freezer and allow to freeze for another 40 minutes.
When ready to serve, scrape the mixture with a fork to create icy flakes. Scoop the granita into serving glasses or dishes. Garnish with a strawberry rose if desired.