An issue that probably does not get discussed enough is the larger the number of files in the library, almost assuredly the greater the amount unidentifiable content. And therein lies the rub.
This should be required reading for those who want Roon to import and manage unusually large libraries filled with unofficial or non music content. It is one of the best Support responses. Ever. Because it is unapologetically direct as to what Roon is and is not designed to do.