Rome was a center for traders and visitors from all parts of Europe and the Near East not only during the Imperium but in Late Antiquity and the early Middle Ages as well. It's a big mistake to assume they're all locals.
Indeed, when the samples were analyzed autosomally it was clear that some of the samples from Late Antiquity and the early Middle Ages were northerners visiting the city.
As Geary did with the Langobard cemeteries, the samples should have been analyzed with isotopes, which would have made their status clear to everyone and not something we have to figure out for ourselves.
Italians have not changed since the early Middle Ages, especially in Rome and the more northern areas, and those percentages are too high.
That said, blue eyed people do exist, and in quite high percentages in some parts of the country. In the Veneto, for example, more than 40% of the people have light eyes. In my father's area in the northern Apennines, in some villages, including his, everyone is light eyed. (Of course in the mountains drift plays a big role.) In the more northern parts of Liguria the same is true, almost always paired with dark hair, but not always.
Miss Liguria:
Indeed, I recall a study from years ago that a very large percentage of Italians are heterogeneous for light eyes. Of course, that doesn't "show".
This is, I think, the combination to which you referred, and that is quite common in Ireland and Scotland.
Percentage of light eyed people in Italy:
Percentage of blonde haired people in Italy:
This is the best map ever made since it is based on a study done at the end of the 19th century before the vast migration from south to north, and they used tens of thousands of army conscripts.
Aosta and Trentino have many non-Italians so the data from those two areas is of limited usefulness.
Anyway, again, you can see the disconnect in percentages between light eyes and light hair.