In fact, I think it is bad technique. That is why I never taught it in my Kimura Trap System.
Instead, I favor the Diving Kimura. It sounds similar, because it is.
The main difference is that we are aiming for side control and using our hips to smash our opponents chest or face. Whereas with the Rolling Kimura, you apply no pressure to your opponent with your body and leave a lot of space for escape.
This video goes over the proper execution of the Diving Kimura, and why the Rolling Kimura is flawed. Watch this to tighten up your acrobatic Kimura catches and keep your opponents guessing.