The Workbook is a minimal system installed both on AROS 68k and AROS x86, to start it you just have to modify the Startup-sequence, in fact you have to disable the Wanderer boot and instead use the famous LoadWB.
Regarding the Rom, the WinUAE ones are not up to date, the ROMs are updated every so often and to avoid mistakes you have to use the ones included in all the Nightly Builds or Distributions!
To learn more about Workbook read
HERE