Watch the Basic 4-Note Roll online guitar lesson by TrueFire from Americana Greatest Hits
Lesson Source: Ben Wright's Bluegrass Banjo for Guitar Players
This is a 4 note roll exercise with the metronome that you can play along with. Very early in my playing (like a month) I showed up at a party with a couple people playing some blues on guitars. I sat down and followed their progression with this easy roll and it blew people's minds. The sound of this instrument catches people in a really unique way and you don't have to be a master to make it sound good.