AfaIk, the Romans used a dot • for indicating a multiplication. So if the dot is missing, it’s an addition.

Real in math means it is, let’s call it, normal countable number, as shown with the one guy on the left side.

Imaginary numbers are a mathematical concept which are based on i. This means that if i is squared it equals to -1. This is not possible with real, in a mathematical sense, numbers, because there, if something is squared, a positive number is always obtained. The guys in the middle have the i and are therefore imaginary.

Complex numbers are combining mathematical real and imaginary numbers, as shown by the chaps faces on the right side.

Now what is the connection to the meme?

My interpretation is that the real Romans are those everyone knows and nobody denies, like with real numbers.

That is the only one I’m pretty sure about, the others are less clear to me.

The imaginary ones could mean that they are wannabe Romans but that scholars deny it or that they are Romans, but publicly not seen as such, hence the imaginary part. I can’t identify their armors.

Complex Romans are in analogy to the numbers those that are partially real and partially imaginary. I identify a Byzantine armor, whose empire resulted from the eastern part after the division of the Roman empire. So that would mean they are Roman, but it is complex, because they are not what most people imagine when they hear “Roman empire”