MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
A rumba board has 6 steppers may be you can ad this https://www.reprap.me/stepper-expander-x3.html you have 9!
https://forum.e3d-online.com/threads/adding-a-fourth-extruder-to-the-rumba.1892/ more info
https://reprapworld.com/products/electronics/ultratronics/ultratronics_pro_v1_0/ an other board with standard 4 extruders.
info about smoothie board and multiple extruders http://smoothieware.org/multiple-extruders
So and now go figure it out and report back when it works ;-)