question about drum rolls

I can do a drum roll, but how do people do those super smooth rolls and do little fills off that roll. When ever i try doing little fills off my roll, I can never smoothly change back into the roll smoothly and it sounds sloppy. if you don't clearly know what im talking about watch like 30 secs into this clip.
http://www.youtube.com/watch?v=1bIchqJoxFQ