I don't think it would be too difficult to explain to them what technology does. How technology works, on the other hand, would be near impossible. Same goes with most science and medicine. Explaining the what would be much, much easier than explaining the how.

I think the hardest thing for them to grasp is the fact that all forms of people are, in most places, equal. Nobody can force another person to do something against their will without potential punishment. There are still social and economic classes, but they all have the same rights. I think the case would be stronger if it was a Roman born into privilege. It would be quite a blow to find out that they are no longer as special as they think they are