"I know the rompath is right"
....well....I would say...no, it's not ;-) So, please give details how your files are arranged. As mentioned in a previous post, checking snapshot dats is easy since it follows the general standards, however, the rompath/folder structures may look a bit weird.
The titles datfile (not including software lists) got 1 set named "titles", so you got somewhere a folder named "tiltes" and this folder contains the single *.png files. Or you got a 7z/rar/zip archive named "titles.7z" (.rar/.zip) which holds the single png files.
Now the rompath you need to setup is the PARENT folder which holds either the titles folder or the archive file.
This follows the general rules:
rompath\setname\filename 1... filename n (for decompressed sets)
rompath\setname.zip (.rar/.7z) (for compressed sets where the archive holds the single files)
So double check your setup.
If you're still sure the strucute is correctly setup, you might use a wrong datfile for right files or vice versa.
"The ROMS being referred to are standard Winzip documents" ....sounds weird, since for titles you only need 1 archive, not multiple (as long as you don't include snapshots for softwarelists).
Generally speaking, you need to describe your setup a bit more.....one time you talk about tiles, one time about roms and your free text error message does not make sense either.