I owned an organic root beer business for a while. Though I cannot divulge the secret company recipe, I did learn quite a bit about the Sassafras root.
It was banned from consumption based upon a single animal study. Inquisitive as I am, I turned up this study, which was performed on some poor rats. My research is currently thousands of miles away from me, but if I remember correctly, they injected the little guys with enough sassafras to equate to an average sized man drinking inhuman quantities of rootbeer every day...I want to say like five gallons a day. Consumed in normal amounts it wasn't any more dangerous than eating an apple every morning. Hey, isn't that supposed to be good for you?
Anyway, I would look into yourself, rather taking the FDA at its word. People have been eating or drinking the root for thousands of years. The FDA has only been stumbling over itself for the last hundred.
I tried making a few batches with some personally harvested root, which were great. I also tried batches with the bark, which were not great. Safrole, the stuff they say will kill you, is much more concentrated in the root, and as far as I can tell, entirely responsible for the delicousness and fragrance of old fashioned root beer.
That said, there are hundreds of things people have thrown together and called rootbeer. If you can manage to think outside the usual consumer norms, root beer can be pretty much anything you want it to be. Hell, I've seen some old recipes that would do a lot more than give you cancer.
I'm sure I sound like a delusional cancer crazed sassafras lover, so I'll try and post the study If I can dig it up again.