Ouroborialis is FREE in the Roku Channel Store.
After purchasing Ouroborialis, you need to go into your Roku Settings, select "Screensaver" and then select Ouroborialis. On the Roku2 you do this by clicking left or right until the word "ScreenShades" appears.
Make sure that the screen does not say "disable screensaver", if it does, move to the "Wait Time" section and click left or right to set a time for the screensaver to appear.
Then click down on your remote until you reach the "Save" selection and click the OK (or "Select") button on your remote.
Ouroborialis should now be enabled and will run when your Roku is not being actively used or paused in the middle of a video.