Radio Boss USB uses the FTDI chip for USB interface.  This chip is the most common in COM port applications and comes installed already with many of the newer OS versions.  Many other amateur radio products use the same device, so even if it didn’t come installed, you may already have it anyway.

However, if you need the drivers, the latest official versions are available directly from the FTDI chip manufacturer with no hassle.
  
http://www.ftdichip.com/Drivers/VCP.htm

There are separate drivers for Windows, MACs and Linux.

Install the driver first, then when you restart and plug in Radio Boss, the correct selections will appear as a driver, or a COM port.