Spatha, cAD300

[Flavivs Aetivs]

The two blades on the Comitatus website you posted Nathan are a Germanic Type-I Spatha, which is a pretty generic typology that ranges over several centuries, and the bottom one is Roman, of the same type as the 4th century Cologne example but with lenticular blade and a simpler hilt.

The Germanic Type-I is what eventually became the standard Roman Spatha: we can see this in Roman blades like the Feltwell, a Roman munitions blade dating to about 400 AD, which is very similar to a Germanic Type-I. The later Pouan example appears to be basically the same as the Feltwell, but far fancier and better made. By the time of Justinian, the Germanic Type-I is the standard Roman Spatha.

So yes, either of these blades could be used interchangeably: the Germanics ended up with quite a bit of Roman equipment circulating through Barbaricum, and the Romans sometimes adopted foreign influences in their military paraphernalia.