I'm a bit confused by the comment on roadmap not navigating subdirectories. Both roadmap4maemo and upstream roadmap navigate subdirectories fine.
from my N810:
Nokia-N810-23-14:/media/mmc1/roadmaps# ls
CA IL NJ NY usdir.rdm

I _do_ think that the usdir.rdm file needs to be at the root, but this is a separate download from the state maps anyway.

WRT the earlier question on why roadmap doesn't ask for city when searching by intersection (only state and roads) - it prompts you with a choice of cities once the search is performed - IIRC this has more to do with the internal storage format of the maps than anything else. Although it is not exactly identical in function, the maemo port is very close to the upstream project - I highly recommend browsing through the manual: http://roadmap.sourceforge.net/manual.html

The UI is very configurable and a lot can be done to make it more friendly to A: using while driving (screenobjects) and B: the N8x0's really tiny dotpitch (sprite scaling factor)

HTH,
wisp