Just wanted to give an update. I took the case off the retrode and was able to successfully dump the ROM. Haven't played it too much yet, but when I started the game in an emulator it gave a bad checksum error but seemed to still play.
For the record, the ROM included in the version sold on Steam also gives a bad checksum error and I'm pretty sure that's intentional because this is what
ucon64 has to say about it:
Checksum: Bad, 0xbf8b (calculated) !=
0x0000 (internal)Inverse checksum: Bad, 0x4074 (calculated) !=
0x0000 (internal)(It looks like they just didn't bother to calculate a checksum while mastering, since it wasn't necessary to get the thing to boot in a real SNES.)