Yup. Learn to use
ClrMamePro proficiently, and you will do yourself (and us!) a huge favor. If you knew how to use
ClrMamePro, you'd be able to tell all by yourself, within minutes, exactly which ROMs have been updated or changed between ANY two versions of MAME.
Aside from that, anywhere from 15-50+ ROMs can change between versions. Now, whether they're changes worth worrying about or even changes to games you'd play is, for most people, the deciding factor on whether to update or not.
As Peale said, there's no reason to upgrade/update either MAME or your ROMs if you're perfectly happy with what you've already got.
-Steve