I'm pretty sure I can answer that one
A "rough transcript" is what a court reporter or closed captioner will insert as a header so as to let the reader know to expect mistakes, misspellings or words translating incorrectly.
It's commonly used during "real-time" translation or closed captioning, any situation where a stenographer or voice writer is using a computer software program to instantaneously translate voice to text.
As a court reporter, I use that header all the time in court for my own transcripts. During the day in court, the attorneys will have my transcript coming up on their laptop screens as words are being said. It's a "rough draft" because it is rough. There will be misspellings, proper names might come out in steno (much like what I've written above my avatar) or not spelled at all, quotes will need to be verified with documents read from, etc. After a day in court, I'll come home and edit every page of that transcript until it's perfect. Then the final transcript will go out without that header, and I'll certify it.
Closed captioning is very similar -- although there's not much of a second chance to make it perfect later. But I can understand in this situation why a reporter or captioner would use a header. We don't want anyone "citing" a rough draft.
HTH