An Eight Note Pattern
This eight note pattern is an essential part of Scruggs style picking. For learning purposes, let's split this up into two phrases of four notes.
The first phrase will be the forward part of the roll, which is played on strings 3215. You're starting with your thumb on the 3rd string for this part. Next, you'll play 1231. This is the backwards section of the roll. Practice both of these parts separately and then put them together when you are comfortable.
Forward/Backward Roll Video Tutorial
Play along slowly with this tab to practice the forward/backward roll.