Here is a working first pass at making DCW maps with world-wide coverage. The DCW map data used for this as been split into smallish tiles to facilitate is use on PDAs. The current integration with roadmap is by giving each tile a fake state-county fips codes. You will need a recent (after 25 Oct 2004) copy of CVS to get this to work, because of some resent changes that have been made to fix some bugs and to support this. The following image shows how the tiles map to spatial areas.
You can download all the data via this tar file: dcw-maps.tar.bz2.
If you would like to browse the maps that I extracted the roads from you can take a looks at vmap0 map browser. You will not see this level of detail in roadmap as I only built the roads layer.