I'd expect any SE/Plus ROM combination to fail. The significant differences between Plus and SE are ADB and PDS, although I imagine there are tweaks around serial and sound too.
PDS required that the SE had a Slot Manager, and Slot Manager is found in ROM code for all Macs based on "NuBus architecture". A Mac doesn't need to have NuBus slots to use NuBus architecture; the latter was employed in PowerBooks and the LC family. In the SE, Slot Manager is going to juggle all of the memory addressing and introduce new hardware interrupts, so it is unlikely to work with earlier models.
Think about the two Mac Portables: they demonstrated that a 68000 Mac could have a useful amount of RAM and you could even hook up to an expansion chassis with SE PDS cards, but the ROMs introduced new hardware compatibilities for those cards.
PDS required that the SE had a Slot Manager, and Slot Manager is found in ROM code for all Macs based on "NuBus architecture". A Mac doesn't need to have NuBus slots to use NuBus architecture; the latter was employed in PowerBooks and the LC family. In the SE, Slot Manager is going to juggle all of the memory addressing and introduce new hardware interrupts, so it is unlikely to work with earlier models.
Think about the two Mac Portables: they demonstrated that a 68000 Mac could have a useful amount of RAM and you could even hook up to an expansion chassis with SE PDS cards, but the ROMs introduced new hardware compatibilities for those cards.