I’m hoping to find this show so I can watch it, but my poor search strategy isn’t yielding anything yet.
It was on network TV, before cable. Could not have been earlier than 1977 [ETA: 1976?], could not have been later than 1983. Likely was very close to 1980. It aired in the winter (I remember snow on the ground).
The subject matter was the origin of rock and roll music. I have no clue as to the actual title. I’m pretty sure it was a single-episode special, not part of a series. I expect it was one or two hours long.
Quite close to the beginning it talked about Hank Williams. That’s as far as I got before having to leave. I’d imagine Hank was about 5 minutes in, could have been a bit less, virtually certain it was before the 10 minute mark. I was surprised and intrigued that Hank was being tied to rock, but I didn’t get to see the rest of the show.
I know it doesn’t quite match your memory, but The Roots of Rock ‘n’ Roll was a documentary series consisting of 6 one-hour episodes that aired in 1980 and/or 1981. I can’t find a lot of information about it. IMDb lists only the narrator and hosts but surely they must have used a lot of archival footage that isn’t credited there.