What EnTerr said is fairly accurate. Components such as roCompositor, roRegion, roScreen, and roSprite "cannot be used in a Scene Graph application", according to the Scene Graph XML Guide section on
BrightScript Support. Those components are part of the 2D API, which is commonly used in developing animated game channels. The 2D API uses an roScreen component as its screen canvas. While it may be possible (*) for a Roku application to use multiple screen canvas types (standard, roScreen, and roSGScreen), only one screen canvas can be active at a time, so you can't put an roSprite onto a standard canvas or an roSGScreen canvas, for example.
Scene Graph provides an alternative way to design a user interface. It is neither more "correct" nor less "correct" than using standard components or 2D API components, nor does it supersede previous components. It's just different (and newer), not necessarily better for every situation, and certainly not intended for all the things. Use whatever you deem to be most appropriate for your specific application.
If you are animating images or shapes that you can construct from Scene Graph components (rectangles, labels, etc.) than you may find the Scene Graph Animation components useful. If you are creating your own custom bitmaps somehow, then the 2D API (roScreen) may be more appropriate. You may even find it easier to use standard components (roImageCanvas) to construct your UI if you're not looking for high frame-rate animations.
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(*) I'm not trying to suggest that you try this, just that I know from experience that it's possible in certain cases. Roku does not officially support, encourage or condone mixing screen types.
