AHC/WI: More Roman ruins in northern Europe during Middle Ages

Let's say that the early Roman Empire had expanded well into the Netherlands, Germany, Poland, and Ukraine, expensively building many stone buildings, paved Roman roads in very muddy areas where road building was difficult, as well as a largely futile, but monumental "Great Wall" against the Germanic tribes. There are several additional Trier-like cities as well. The Roman provinces of Magna Germania and Sarmatia are transient but last as long as Dacia and see further incursions. When the Roman empire collapses, convergent tribes take over the same areas by coincidence (I know, butterfly decimation, but let's assume ceteris paribus), Abrahamic religion still predominates. How do the Early and High Middle Ages proceed with far more Roman ruins and stone buildings available in the cooler, wetter parts of the European continent?

Bonus scenario: We could go further back and Phoenician or Greek colonies (and remaining, derelict large temples) could be present as well.
 
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