First of all, all credit goes to this guy's blog: Make the Edirol or Roland UM-1 and UM-1X work on Windows 10 | Zodiacal Light

Basically you need to download the 8.1 drivers (32 or 64 bit as appropriate), then extract the files.

Then search the extracted folders for RDIF1009.INF or something similar. Modify the .inf file so all occurrences of "NTamd64.6.2" become "NTamd64.10.0". Then manually install the driver by going to device manager, right clicking on the "unknown device" (specifically the one with hardware ID USB\VID_0582&PID_0005) and "update driver...".

If you are running a 64-bit OS make sure also you have disabled driver signature enforcement.