Hello...This is my first time posting...but I thought I'd turn in my $.02 worth. I think that a good practice would be just regular forward rolls...but focusing on the ability to control the speed of rotation. This obviously comes in handy when being thrown from a "high throw" (e.g. koshi nage) or "low throw" (e.g. sumi-otoshi). Just for example...you would not want to rotate too quickly when receiving koshi-nage.