Joe. You are quite right. The sample of Rosie in question comes from Lomax's field trip to Parchman Farm in November 1947. It was issued in the USA on a Tradition LP called (I think) Negro Prison Songs, and in Britain as Murderer's Home before being reissued by Rounder as part of the Alan Lomax Collection.

However, I don't agree that the other Rosies you refer to are different songs. To my ears they are all versions of the same song.

Indeed, I've seen a version somewhere (in Slave Songs of the United States by Allen, Ware, and McKim Garrison, I think). Which would suggest that it's a pretty old song. Well, by African-American standards at any rate.