Add the dried roses, sugar, and water to a small pot and simmer for 10 minutes over medium-high heat. Bring the mixture to a low boil then reduce the heat to low and continue to simmer until the liquid thickens. Remove from the heat and let it cool before using it in the cocktail. You will need to strain the syrup to remove the rose petals.
Making the cocktail
Add the ice, gin, rose simple syrup, and lemon juice to a cocktail shaker or mason jar. Cover the shaker and shake well for 10-15 seconds. Strain the cocktail into a coupe glass and garnish with a lemon slice and dried roses.
Making a Mocktail
Add the ice, simple syrup, and lemon juice to a shaker or mason jar. Cover and shake for 10-15 seconds. Strain into a coupe glass and top with soda water or sprite.
Store the simple syrup in the refrigerator for up to 2 weeks.