Watch the Banjo Rolls: Study 2 online guitar lesson by Jason Loughlin from Country Guitar Survival Guide: Lead Edition
This instrumental study introduces us to backwards rolls, which means we are rolling from high to low on any set of three strings. Just like with the forward roll patterns we will focusing on rolling through seconds and thirds, although with this example I've also included some triad shapes. This will give you a good idea of what you can do in keys where the open string notes are dissonant.
When you feel you understand both techniques, try writing solos that mix forward rolls and backwards rolls together.