Bring water and sugar to a boil in a small pot, stirring until sugar dissolves into a syrup. Stir rose water, cardamom, and saffron into the syrup. Reduce heat to low; cover to keep syrup hot.

Melt butter in a large saucepan over low heat. Stir in flour until mixture is a smooth paste, about 1 minute. Cook, stirring constantly, until paste turns brown, 10 to 15 minutes.

Remove flour mixture from heat. Whisk in hot syrup gradually until syrup is completely absorbed and mixture is the consistency of a smooth, soft paste, at least 4 minutes.

Spread mixture in a shallow bowl. Cool to room temperature, about 20 minutes.