Hello Arthur
Channel 4HD is encrypted and currently only available on satellite if you have a Sky subscription. I think it's inevitable that will change eventually but for the time being you can't get it.
Channel 4SD has a number of regional variations to allow advertisers to choose which parts of the country they want to be seen in. I am not familiar with the Ross box itself so I don't know how you go about selecting your channels, however the information you need in order to choose the right version of C4 for you is all here:
http://www.flysat.com/28east.php