I was just watching an international game between the best USA high schoolers and international players. It made me google international officiating. I ended up coming across a video that seemed pretty good regarding 3 person responsibilities. I'm not sure if we use exactly the same rotation etc., but this video seemed like a pretty good explanation of responsibilities for 3 man. I think it reinforces that we should call our primaries and stay the hell out of everyone else's!
FIBA.com - Referee corner: Videos
Cheers!