If there was any connection between later roman shield designs and later western europian heraldry it was probably only small as real heraldy only emerged some 5th centuries after fall of the Western empire and art of Heraldry although known in "Byzantium" via western knights on crusades was never completely accepted by the Byzantine time Romans.
Hey, the way of fighting of the classical Legion was pretty dead by then, wasn't it? I mean, the typical quinqux, triple axies, duplex axies, etc. I know that Diocletian and Constantinean reforms meant to flexibilize the army, but didn't it lose a bunch of it's power in hand to hand combat against the barbarians? The abandon of Gladius and traditional Scutum, etc. Enlight me, please. By the way, terrific art!!!