Numerous times throughout the site I've seen the topic of the Roman legacy versus the Germanic legacy. Here is a nice forum to discuss it.
Here is a link that will serve as a nice backdrop: encyclopedia.lockergnome.com/s/b/Germanic_tribe
The Germanic tribes were either absorbed by the empire or overran the empire, depending on which scholar you ask. But one thing is clear: with the collapse of central Roman authority in the West, various Germanic tribes and their successor kingdoms sprouted everywhere.
The Germans internalized to some extent the tradition of Roman imperial government and Roman law, and eventually the new Roman religion of Christianity. Thus the Germanic tribes in continental Europe helped to pass down the Roman legacy. Indeed, in one way or another, whether as friend or foe, they had been subject to the Roman legacy for generations.
However, the further away we get from Rome itself, the less of an influence we find. This is particularly true in the lands that would become Britain, where the Germans retained their tribal common laws as opposed to Roman legal codes. The people of Britain, who were only partially Romanized to begin with, were closer to the Germanic culture. Under German occupation they became more Germanized then they had ever been Romanized. This is why England and its former colonies arguably owe as much in law and government, culture and language to the German heritage as they do to the Roman.
As a side note, UCLA professor Eugene Weber has pointed out the line between Protestant and Catholic Europe is roughly the same as between the Roman Empire and the unconquered German territories, evidence that cultural legacies dictate religious development.
To what extent did Rome influence the various Germanic tribes? To what extent did the various Germanic tribes influence the decaying Roman empire? And how should we rate the impact of each group on the development of Western culture?