FKMA,
There is a lot of info and pictures on
http://www.rolandus/RUG/ARCHIVE/SUM_97/FEAT15_1.HTM/BG_A90.HTM
Nice pictures on
http://www.rolandcorp.com/japan/products/mi/A-90EX.html
Pictures of the Expansion Boards and Memory Card on
VE-RD1, VE-GS1 and M512E
http://pt.roland.dk/catalogue/cgi-bin/prod-main.cgi
VE-JV1
http://it.roland.dk/catalogue/cgi-bin/prod-main.cgi
I think that it will be hard to find editors, as the boards are almost non patch editable.
You have access only to performances ...
Regards,
Fernando Justo