There actually is a way to exceed the map size limit in ROC.
Firstly you need to understand that you should be playing FT... But assuming you have it and you want to make a map for old schools sake... I would suggest that you go to the download section and pick up WE Unlimited, (I"m pretty sure that works with ROC) Upon dling that and applying it to your warcraft you can do alot of stuff afterwards. I believe the maximum limit for WE is somerwe lke 5 hundred something or maybe even more ?? but there you go... and sorry wolf