Ahhh... I had (briefly, occassionally, and never enough to bother finding out the answer) wondered what root beer was -- I presume it's primarily a US thing, as I've rarely seen it in the UK. I'd assumed it was akin to ginger beer rather than to ginger ale.
Personally, tonic water -- lots of tonic water. No malaria for me!
Rootbeer = TCP medication in a glass - same taste anyway - yummy!