That's an odd question considering that over half of the Roman emperors were not from Italy. From the 3rd century onwards, the majority were from the Balkans (including the Tetrachs and the Constantinian dynasty). Some were from Spain (Trajan, Hadrian, Theodosius), from North Africa (Macrinus, Septimius Severus), mixed North Africa and Syria (Geta, Caracalla), Syria (Elagabalus, Severus Alexander).
If you refer to early emperors of Patrician descent, it's hard to tell because Rome was multicultural from the start. It wasn't purely Italic (Latin and Sabine), but also incorporated families of Greek and Etruscan descent. But considering that the Etruscan appear to be autosomally similar to Italics, and that the Greek ancestry was the lowest in the lot during the Kingdom and Republic, I'd say that Republican patrician and plebeian families from Rome itself were most probably like the Iron Age samples in this study, but plotting slightly more south toward southern Italy.