A bit buggy on older laptop with older graphics. Got USB ports working by regedit.exe in the bottle, get to software items and under /wine/ports define COM1 as string key and assign value of /dev/ttyUSB0. Same for COM2, etc.
Got Rotor.exe working ok. WinkeyUSB is still an issue, not working reliably.
Crossover seems to come with 32 COM ports pre-defined. Adding USB device creates COM34, COM35, etc even when registry maps COM1 to /dev/ttyUSB0. Both definitions (COM1 or dynamic COMxx) seem to work, but why then reserve 32 COM ports in the first place? It may be a Wine issue.
N1MM+ seems to have some issues saving the configuration. Every time the config (ports, etc.) comes up, it always sets SO2V, even if one sets SO1V and saves it.
With old video hardware, change wine settings so Wine does "not" manage the windows. Yet to test on newer machine.