This iron arrowhead is not Roman, it is rather early medieval. Look at this plate : Arrowheads from the Reihengräberfeld of Bülach in Northern Switzerland. 6/7th cent. Source: Werner, Joachim: Das alamannische Gräberfeld von Bülach. Basel 1953. Plate 38 I think your arrowhead is paralleled by nr. 3 and 4 in this plate.