The Rosedale verse that Cream used is actually from another Robert Johnson song called "Traveling Riverside Blues". Actually the last line is "You can still barrelhouse, baby..." And I'm pretty sure Clapton sang the last verse the same words as Robert Johnson did. This verse is integral to the movie "Crossroads" which featured the song. However, the movie got it wrong--they had Willie Brown being a harmonica player. He actually was a guitarist that played a lot with Charlie Patton and Son House. Young Robert used to sit around and watch them and try their instruments when they went on a break. Willie was the author of "Future Blues" which I believe I'll go post on the favorite blues thread.

BTW, I consider Cream's recording to be perhaps the best live recording of a song in the history of Rock 'n' Roll. But that's just my opinion.