“Roll over” is a great confidence builder for shy puppies as puts them in a vulnerable position for a moment — but nothing bad happens — and they recover on their own steam.
It is very easy to teach using the method of food luring. To begin with, start with the pup in a lying down position and use the food to guide the head backwards. This will throw the body off balance and pull it over on its shoulder. As the pup flops onto her side, continue to guide the head and then reinforce (with praise or a click) when she is on her back. Allow the puppy to right herself, and then treat.
The great thing about roll over is, as with the spin, you only have to train half the behavior and the dog does the rest on her own.
The roll over is easiest to teach when it is always in the same direction. Therefore, the puppy has to be positioned correctly in order to be successful.
Once the behavior is learned, the gesture can be faded to a slight hand cue or verbal cue. While practicing, it is okay to let the puppy have fun and play around. All the excess paw flipping and shenanigans will eventually disappear.
It is worth mentioning, though, that there is some controversy over teaching a dog to roll over, especially among the large breeds. The fear is that it will contribute to bloat or torsion, where the stomach flips. I understand the concern but this has never been my experience. All my dogs learn roll over as a trick and it is one of the first things I teach them. They roll naturally in the yard when on their own anyway.
For more information about puppy training, check out my book, 25 Ways To Raise a Great Puppy.