The most significant argument against dating the origin of the Old Testament writings in pre-Roman times:
the Old Testament text genres are Greek inventions that did not exist in pre-Hellenistic times in Palestine.
The Greeks invented the epic, tragedy, philosophical dialogue and novel: all new literary forms that did not previously exist in literary history.
The Greek love of narrative, the art of rhetorical expression and literary forms were completely innovative. They were widespread in Hellenistic times and copied by the Romans in particular, but also by the Jews. Romans and Jews each used their own languages: the Romans wrote in Latin, the Jews in the revived language of Hebrew.
The Old Testament should be read as a roman à clef about the time of Herod.