There is an excellent thread on medieval perceptions of Roman ruins by /u/sunagainstgold and /u/aldusmanutius.

Medieval authors did not typically think about Rome in terms of technological difference, but it's far from clear that Rome was a "far more technologically advanced society" in the first place. See in particular this thread, where /u/alriclofgar does a really excellent job of contextualising how technological changed into the early Middle Ages, and why thinking about this as a matter of scalar progress or regress is unhelpful.