Lane Chandler and Jack Rockwell are in studio records/casting call lists as cast members, but they did not appear in the movie. Neither did Bob Burns and Jack Kirk who were listed as cast members in a modern source.
There are over 100 songs with the title "Red River Valley," virtually all based on the public domain, 19th century version that is often played by country-western artists and in movies. It is almost impossible to pinpoint any one version, but in this case the version used was published in connection with this movie (a picture of Gene Autry and scenes from the movie on its cover) and was written by Nick Manoloff. The music sounds identical to the traditional version, but the lyrics are slightly modified.