Welcome from Florida!!
You will need to print the Mimaki's crop marks on the Roland. The easiest way to do this is to use a program like Flexi, there was a thread about this (cutting Mimaki prints on a Roland) the other day, use the search button you'll find it.
Also your Mimaki cutter will need an ARMS or similar registration mark sensor in order for this to work accurately. The alternative is to find the crop marks manually, and that's not very accurate.