Certain bad roms appear to run fine, but still are bad roms that have something that is corrupt/hacked etc. that is different to the original rom image. Use a tool such as GoodN64 (available in the download section) to check it. If the rom is renamed with a [!] at the end of a filename such as:
Automobili Lamborghini (E) [!]
Automobili Lamborghini (U) [!]
...you are in the clear and the RDB is wrong (unlikely)
More likely the rom is corrupt and will be renamed to one of the following:
Automobili Lamborghini (U) [f1]
Automobili Lamborghini (U) [t1]
...or not even be recognised at all.