In a small pot, add the ginger root, sugar, hibiscus, lime juice and water. Bring to a boil and allow to boil for 1 minute. Remove from heat, add the lime zest, and let steep for 30 minutes.
Using a fine mesh strainer, strain the syrup into an airtight container and refridgerate until ready to use.
To mix one drink, fill a glass with ice and add 3 ounces of seltzer water. Add 1.5 ounces of rum and 1.5 ounces of the syrup. Stir gently and serve immediately.
For a mocktail version, increase seltzer to 4 ounces and increase the syrup to 2 ounces. Omit the rum.