I could never find a good transfer util ( pref one that would allow a RiacOS hdd plugged into a PC & read under 'doze )
The very frustrating way I did it was to transfer the hdd contents via adfs floppy to the emulated RiscPC. ( VirtualRPC & I think RedSquirel will read native floppies )
The lack of a mouse makes life tricky but don't forget RiscOS is a command-line based OS & the 'WIMP' is just a front-end.
Everything you can do under the desktop has an equivalent in the command line.
Press F12 to get there & if in doubt type: Help ( or H. ) followed by the command you want the syntax for...
The RiscOS command line makes perfect sence but is not much like that on any other computer so you may need to do a bit of head-scratching in conjunction with a manual.
'hope this helps.
Wellcome to the EAB