Just got a used Roland SC-D70 at a very good bargain. It is a fine unit and all, but unfortunately, there isn't any way to change the soundmaps via hardware (like in the case of the 8820 and 8850).
So, I wrote a utility program in Java that sends the sysex messages to perform the sound map change with ease . You can get it here
. Its very easy to use. Simply select the midi output device, the respective sound map and click on the change button.
This program however, requires the java runtime environment which can be downloaded here