I wonder if there were ever any 3.0 ROMs produced for the A500/A2000/A600/CDTV? When I think of 3.0 ROMs it always reminds me of the first A1200's and A4000's that were manufactured before the bugs could be worked out and the 3.0 ROMs were replaced with 3.1 ROMs, but as I did not own any A1200's or A4000's when they were first released, I can't remember how long the time lag between 3.0 and the release of 3.1 was.
@runequester, The A2000 uses only one ROM chip like the A500 and A600 and CDTV (and even the A1000 with an after-market Kickstart ROM board installed), but when AmigaOS3.0 was first released it was only in the A1200's and A4000's which both use two Kickstart ROM chips with half the ROM image in one chip and the other half it the other chip.
As others have suggested, buy a 3.1 Kickstart ROM chip for your A2000 from one of the remaining Amiga dealers and forget 3.0. If your A2000 is not accelerated and has no hard drive, I would suggest that you continue to use your existing 2.0 Kickstart ROM chip. Or you may wish to get a Kickstart ROM switcher and install 3.1 ROM on one side and 1.3 ROM on the other and forget about your existing 2.0 ROM and any 3.0 ROM chip you have or are thinking of getting.