I was told to look over my left (I ride regular, and I'm referring to a hs cut). I learned the backroll by doing this fine, it took a while, but now I do it a little different. I kind of cock my head towards my right shoulder while I look towards the boat/horizon. When I was looking over my left shoulder, I did it a little too dramatically and it caused me to rotate off-axis a little.
I guess what I try to do is raise my left shoulder, and dip my right shoulder, while at the same time almost touching my right ear to my right shoulder (while looking towards the boat though).
Hope that helps some.