Add the first 4 simple syrup ingredients to a small saucepan and bring to a boil, stirring, until sugar has dissolved. Strain and allow to cool. Add rose water, stir gently to combine and pour into a sealable container. Store in the refrigerator until ready to use.
Pour all cocktail ingredients into a cocktail shaker along with 1 cup of ice.
Shake for 15-20 seconds.
Pour into a glass over ice. Garnish with fresh blackberries and a thyme sprig.