The article didn’t say “race” at all. Its wording tries to simplify, for a mass audience, the research that found at this Balkan site DNA that is mainly associated with sites in the east of Europe. Across archaeology and linguistics, there has been an archaeogenetics revolution in the last 15 years or so that enables tracing historical migrations like never before.

I don’t know why you think “attracted to the wealth Rome invested in its frontier zone” is a wording that implies jobseekers. It can obviously mean opportunities for pillaging, which peoples of the Eurasian steppe did for centuries. It can mean making use of convenient infrastructure left behind when the Roman military retreated from certain holdings.