I wouldn't worry about it. First of all, Bernie and Mark were researching an SS member rather than an SA member. The SA files are not mixed with SS files in the National Archives or German archives. Plus,it's possible that they were checking DAs instead, in which case it's even possible that there was an SS member Otto Roth, as not every person attached to the SS was in the DA. I agree with Trond, that there is no reason to suspect the piece is fake just because earlier research for an SS Otto Roth turned up nothing.
Erich