Rolls are a very important part of thumb and finger style guitar, from Merle's two down-one up rolls with thumb and index, to Chet's elegant two and three finger rolls, to Jerry's banjo-inspired backward and forward/reverse rolls, to Lenny's three and even four finger patterns. Any fingerpicker would do well to study the accompaniment roll patterns of these masters, including Paul Yandell, who learned literally at their feet. (Just listen to Paul's accompaniment rolls behind Chet on the Chet Atkins Picks on Jerry Reed album, as well as his own body of work.)
Chet did use the PMI (thumb-middle-index) pattern, but many others as well. Don't think of the roll as carved in stone- Chet and the others would alter the sequence (and the fingering) to get the notes they wanted. The pattern was a means, not an end.
Transcribing and learning many of Chet's, Jerry's, and Paul's tunes will give you the equivalent of a master's degree in fingerpicking, and I'm still learning every day. Guess I'd better close for now and get back to work on that Reed roll that Paul showed me.
Craig
P.S. Before Jerry came along, Chet used mostly the forward roll and variations. Jerry told me that he got a lot of ideas from banjo players like Bobby Thompson and Larry McNeely.
