Ethnicity of "Roman" soldiers

[Sean Manning]

Could anyone point me to any works - books or articles - that have information on the known ethnicity of soldiers in Roman units (probably via their names at a guess)?

By preference the east post Septimius Severus.

Thanks in advance.

Its trickier than you might think to identify ancient people's ethnic identities. For example, some people take names from the dominant culture in addition to the one they were born with. And I have an Irish name, but that doesn't mean I think of myself as Irish. Sometimes ethnic identifications in records have more to do with the government's ideas about how to categorize people than the ideas of the people recorded. (The Ptolemies in particular seem to have used ethnic labels this way, but think of “Blacksâ€