As a "folksy" drink, it's actually been something of a challenge to get a reliable root beer recipe. I've found countless recipes for home made ginger ale, but a lot of root beer recipes just recommend using a liquid concentrate for "home brewed" root beer. Although just mixing in a bottle of flavoring and sugar seems more like making Kool Aid than a real homemade drink.
I think a big part of the trouble with home brewed root beer is that it's hard to lay your hands on the ingredients. You can buy ginger at any grocery store for ginger ale, or lemons for lemonade, but root beer is an odd mix of eclectic and hotly-argued ingredients. Some people say you just need the (confusingly similar sounding) sassafras root and sarsaparilla root, mixed with sugar and yeast, while others recommend adding things like chopped fresh ginger, birch bark, wintergreen oil, vanilla, licorice root, molasses or star anise.
Slapping one more layer of complexity on this is that while some herbal shops do sells sassafras, it's the bark (the leaves are used to make file powder), and not the actual roots. While some people say they can be used interchangeably, some say the bark doesn't deliver the same root beer flavor as sassafras root. So with my head thoroughly overwhelmed with online hearsay and out-of-print cook books, I decided to hold off on the root beer.
Then in a moment of serendipity, a lady at the local farmer's market was selling sassafras root as a "Spring Tonic," along with her pork and vegetables.
So long, confusing story short, I'm back in the root beer business, baby! Updates to follow in about 5 days, once it's ready to drink.