Can you give more information on why the randomiser program isn't working? It would make the whole process a lot easier.
Are you using the randomiser tool? When you first run it, it creates a folder in your Documents called "colosseum randomiser". In that folder there is a folder called "ISO". Put your ISO file in that folder. When you click save on the randomiser tool, it will import the changes to any file in that folder with a ".gcm" or ".iso" file extension.