Roger as in "roger that ... over and out" or Roger with a capital R?
Roger, as in "me"
.
The complete list of tags used for duplicate checking is: title, artist, source, year, duration
We did have length in the list, too, but it got removed to allow for the fact that you might have lengthened the file by changing one of the tags that we don't care about. This was perhaps wrong.
There's several other issues with duplicate detection, as well.
There's a better way to spot duplicates than this, but you'll have to wait until post-v2.0
.