Are you talking about the Roku Home screen or your Application's home screen?
As far as I know, the screenshot utility won't take screenshots outside of a running sideloaded application. I'm confused by you saying "
It will take a screen shot of the main Roku set up on my tv" what is the "main Roku set up", how to get to that screen?It if's your application's home screen you're talking about, could be a bug with the particular roku device (RokuTV?) you're on, I had some problems w screenshot on one Roku TV model. If you have another roku model, try it.
aspiring