To put it simply, all root beers are made with a blend of roots. Initially, root beer was made using a combination of sassafras, but the discovery of its carcinogenic properties led to an update in the blend. However, later research showed that only a part of sassafras is carcinogenic and it's no longer used in current mixes.
Modern root beer is typically a blend of roots, with the addition of licorice or wintergreen to balance the flavors. Sweeteners like sugar are also added, as boiling roots alone can leave a rather bitter taste.
In contrast, birch beer and sarsaparilla are single-root root beers. These are usually present to varying degrees in regular root beer, but in birch beer and sarsaparilla, the unique flavor of the single root is more pronounced. Sarsaparilla is a dominant root in most root beer blends, which is why some people don't notice a difference between sarsaparilla and regular root beer, while others do.
At Tabletop Root Beer Shop, we carry a variety of root beers, birch beers, and sarsaparillas. However, as root beer connoisseurs, we prefer beverages that are closer to natural roots and further away from artificial flavorings that simply mimic the taste of roots.