On my way to pouring a glass of root beer that might have had a bit if rum in it, I started thinking about combining the two ... as an ice cream. So, it's root beer and rum ice cream, AKA, Frozen Black Cow with a Kick. It tastes like a root beer float ... with a little something extra.
Combine all the ingredients in a bowl or a large measuring cup. Stir until the sugar is dissolved completely.
If you're using an ice cream maker with a freezer bowl, chill the mixture completely before churning. If you're using an ice cream maker with a compressor, you can churn right away.
Churn the ice cream according to the manufacturer's directions, then transfer to a storage container and freeze until firm.
If you use this to make a root beer float, I wouldn't object.