The Roman cursive is illegible to modern eyes, as is the archaic script. You may think that the archaic script would be legible once you learn the correspondence, but don't be fooled by their geometric simplicity; they possess a lot of variation in forms (still geometric due to their inscriptional nature) across time and space. Likewise, the modern lowercase letters are likely illegible to ancient Roman eyes. The inscriptional Roman styles have remained legible, because Italic typesetters and printers (see Renaissance Antiqua) have consciously revived the monumental forms for the capitals. (Contrast the ornate capitals of Fraktur, or of English Roundhand).