Hmm... Yeah, the ROMs are the same, for sure.

Floppies... well, for 3.1 and above, I'm 99% sure they're the same, too. (Well, there are actually quite a few small variations in OS3.1 depending on where it came from, but they should all work fine in both NTSC and PAL regions).
The worst you might encounter would be the PAL resolutions coming up as default instead of NTSC. (Booting to a PAL workbench instead of an NTSC one.) This is a very easy fix with the ScreenMode preferences program. (Or, if you can't see the screen, you could just boot with no startup and delete the ENVARC: screenmode-prefs file (I forget it's name) and that will cause the machine to default to whatever mode it runs through early startup in.