Practice your banjo rolls on the banjo until you feel comfortable playing them.
Start listening to banjo music and blue grass CDs and listen to how the banjo player plays the banjo rolls in the song.
Play along with songs with which you are familiar, adding your banjo rolls as you accompany the songs.
Work on staying in time with the music. You should start by playing along with a metronome so you can be certain of playing in time. The worst thing would be for you to be playing your banjo rolls as you incorporate them into the music at a different tempo than the rest of the band.
Experiment with more songs, slowing down the playback if you can. In this manner you can study the incorporation of banjo rolls in the music.
Add improvisation as you move from one banjo roll to the next and incorporate them into music. You'll get better with this the longer you practice.
Accompany a band when you feel confident about incorporating banjo rolls into music. A guitar player who has a good sense of timing is always a plus.