In this arrangement we'll be "riding the 5th string" it's a one way ticket to Bluegrass town. It can also help us play really fast since we're not having to switch strings with our thumb a lot. If you've played the first rolling backup arrangement you may notice some similarities. Yes, the chord changes and form is the same, cause we're still playing rocky top, but check out the right hand pattern. It's still a forward backward roll! As banjo players we need to realize that roll patterns aren't limited to the strings we learn them on. We should try and memorize the picking pattern - TIMTMITM, TITM, etc. - and know that you can apply that to other string sets or even just a single string!
Check out those licks for some embellished Bluegrass backup vocabulary.