All RadControls are included in Sitefinity and you are able to use them in Visual Studio. However, these controls aren't available in the Toolboxes section by default. You can use them to create your own widgets and only after registering them, they will appear in the Toolbox.
The RadRotator is compatible with all Sitefinity versions, so you shouldn't experience problems when using it. You mentioned that it's commented out somewhere. Can you provide some additional information on what you mean exactly?
I also think that you will find this article from our documentation useful, since it covers the steps to creating a RadRotator control in Sitefinity: