The Snake Roll Cast is a highly useful spey cast that can be implemented single handed and was developed by Simon Gawesworth of England and appears on the advanced spey casting techniques video.
This technique seems to allow more distance than the single handed double spey but less than the Tongariro Roll cast. Its advantage and therefore use over the Tongariro Roll Cast is that it can be implemented faster and with less movements. Although possibly harder to do than the Tongariro Roll Cast as the timing is more critical with the Snake Roll, this cast is probably more useful in general situations as it disturbs the water less and will produce more drifting time and less casting time.
To begin with it is easy to set up by doing a single handed double spey but don't put to much punch out i.e. just swoop around (the real snake roll cast was actually developed to save this extra movement but I find it easy and quick enough to put in a double spey and it helps align things easier particularly with the heavy flies and long leaders used on the Tongariro). As the line is coming to touch the water allow it to just touch as you do a short little back cast to create as tight a D loop as possible and developing as little line stick as you can. It is actually easier to watch the below video than to explain. It would pay to look at the single handed double spey cast first to learn the set up for this cast. The whole motion has to be completed relatively fast so that you do not develop much line stick which will kill the cast.
If you are initially unable to view the movie (MPG) file to the right of this (it may take a few seconds or even a couple of minutes to download of you have a slow connection so bare with it a little) then click here. This will hopefully open the application that your computer uses by default to view the movie - after clicking, you may have to check the other open programs as it may not come automatically to the surface.