One of the most interested time periods in history for me is the dark ages. It is interesting to me how western Europe could change so quickly after the fall of an empire. Im very interested to know how people from different places viewed the dark ages. How much did the people in the British isles know about the old world or Rome. From what i know they where hit pretty hard by the dark ages (probably wrong though). How about the people in the Frankish empire, did they know they where living in a very different time compared to Rome? How about people who where never conquered by Romans, the Pictish or North Germans. Was it just another era for Vikings or did they understand the effects too?
A good book for you to pick up is Chris Wickham's Framing the Early Middle Ages. He addresses your question and does so by region (including non-Roman areas such as Denmark and Ireland) as well as thematically (culture, economics, political complexity, etc).
Your question hits on the issue of "decline and fall" - did the West fall? When? The socio-cultural view as of late is one of transformation/continuity. You can see this in Peter Brown, who helped creat the field of Late Antiquity (Dark Age has all these negative connotations). The economic/archaeological perspective is that there was quite a bit of decline (See Ward-Perkins, The Fall of Rome and the End of Civilization). It has to do with perspective: people who view the Roman Empire as normal will see deviation as being a change (for some scholars and elite men, a very Bad thing; but if you were in Denmark and didn't know about the golden age of the Roman Republic, how could it be the Dark Ages?). It's a modern, Roman-centric point of departure.
The Roman age in Britain came to an abrupt end after the Roman removed its army in the beginning of the 5th century to deal with Germanic tribes on the Rhine border in Gaul. The archaeological evidence shows that things reverted to a non-Roman state very quickly, within a generation or two. Conversely, Gaul (especially southern Gaul) remained quite culturally Roman even after Visigoth, Burgundian, and Frankish settlement/expansion into the area. The Romans in the area remained under Roman law, and there seems to be some distinction between Romans and Franks well into the 7th century.
Elite, Gallo-Roman men/clergy like Sidonius Apollinaris and Salvian of Marseille certainly understood that things were changing, and not for the better. But they also clearly were trying to make the best out of a situation (and in Salvian's case, arguing that it was actually better this way).
This section of the FAQ might be of interest to you.