What device for ROMFS ?

Hello,

In a few words: what is the device to be used for a ROMFS root ?

More: I configured ELKS as a ROM image for an embedded system, and I run 
it under EMU86, but I cannot figure out:

1- how to tell ELKS to read the ROMFS superblock from ROM address space?
2- how to build a ROMFS image to put in the ROM address space?

All my tries end up with the well known:

$ ./emu86 -w 0xe0000 -f ../../elks/elks/arch/i86/Image -x 0xe000:0x42 -i

$ ./pcat `cat emu86.pts`
Loading kernel image...
Console: BIOS 10x115 emulating ANSI (3 virtual consoles)
PC/AT class machine, inode! CPU8308K base RAM, CPUID `nd socket for in'.
ELKS kernel (39008 text + 4168 data + 48648 bss)
Kernel text at e062:0000, data at 90:0000 62 K of memory for user processes.
ELKS network sockets
TCP/IP stack by Harry Kalogirou
ELKS version 0.2.0
panic: VFS: Unable to mount root fs on 206D
apparent call stack:
Line: Addr    Parameters~~~~: ~~~~    ~~~~~~~~~~
    0: 1D59 => 0000 7102 0000 0000 0000 0000 0000
    1: 00B7 => 0000 0000 0000 0000 0000 0000 0000
    2: 0000 => CE50 0000 0000 0001 0000 6166 6C69
    3: 1048 => 0000 0000 0000 0000 0000 0000 0000
    4: 0000 => CE50 0000 0000 0001 0000 6166 6C69
    5: 1048 => 0000 0000 0000 0000 0000 0000 0000
    6: 0000 => CE50 0000 0000 0001 0000 6166 6C69
    7: 1048 => 0000 0000 0000 0000 0000 0000 0000
    8: 0000 => CE50 0000 0000 0001 0000 6166 6C69
SYSTEM LOCKED - Press CTRL-ALT-DEL to reboot:

Any suggestion ?

Thanks,

MFLD