Add the lemon juice to a pitcher and stir in the rose syrup.
Fill with ice, top up with water or soda water and stir well.
Taste, and add more rose syrup if desired.
Notes
The amount of juice you get from one lemon depends on its size and how juicy they are. Start with four lemons and add more if needed.You can make rose simple syrup from scratch or buy it online or at a specialty store. Or, mix 6 teaspoons of rose water with ¼ cup of sugar to make your own rose syrup.If you'd like to make this lemonade ahead of time, add the sparkling water just before serving so it doesn't go flat.The amount of sweetness you enjoy can be adjusted by how much rose syrup you add. Test and taste.