I know... my first thought was that he was older, but now that I am thinking about it, I do seem to recall that a lot of the guitar magazines at that time did make it point of pointing out how young he was. He was later than 82 though - mid to late 80's. I saw him while I was in college in Boston somewhere around 87/88. Road House came out in 89, so he was probably 20 or 21 in that movie.
There were a number of hotshot guitarists at that time who were in their late teens/early 20's.