NetworkManager at the moment only seems allows static IP address configuration by the "Static configuration..." option, which apparently means "Don't use roaming mode", or "Don't actually use NM for anything interesting".

This is in many ways not ideal. Notwithstanding the fact that at least on my distribution (Ubuntu Feisty) it then opens a different network configuration tool that doesn't support WPA (and thus is essentially useless to anybody who cares about security) and doesn't acknowledge any of the network configuration I already gave NM to connect to a given wireless network, I think there is a strong case to support static IP address configuration WHILE using roaming mode, either in general or on a network-specific basis.

For example, say I use my laptop at home, at school, at work, at the coffee shop, on the city-wide wireless network, etc.  This seems to me to be NM's intended use case.  Now say that when I happen to be at home, I want to use applications for which I must forward an incoming port to this laptop on my router to make certain applications work well.  This is very common; BitTorrent and a great many networked games for example. Presently whenever I come home, I'd have to switch to the static configuration, and when I leave again I'd have to switch back to roaming.  

It seems to me this is unnecessary: Why not let me set a static IP address when connected to a certain network, and have it remember to use that in roaming mode whenever NM decides to connect to that network?  This wouldn't amount to a profile; it would just be a setting for each network NM has encountered, and with a little thought it could barely complicate to the UI at all (a checkbox in a slightly refactored "Connection Information" dialog could be all).

I know this would be very helpful to me personally and I suspect that a great many other people would benefit from it as well.