These include the kingdoms of the Visigoths (in Hispania and Gallia Narbonensis), the Ostrogoths (in Italia, Sicilia, Raetia, Noricum, Pannonia, Dalmatia and Dacia), the Anglo-Saxon kingdoms in Sub-Roman Britain and finally the Franks who established the nucleus of the later "Holy Roman Empire" in Gallia Aquitania, Gallia Lugdunensis, Gallia Belgica, Germania Superior and Inferior, and parts of the previously unconquered Germania Magna. Additionally, minor Germanic tribes, like the Vandals, the Suebi, and the Visigoths established kingdoms in Hispania.
The cultural syncretism of Roman and Germanic traditions overlaid the earlier syncretism of Roman culture with the Celtic culture of the respective imperial provinces, Gallo-Roman culture in Gaul and Romano-British culture in Britain. This results in a triple fusion of Celtic-Roman-Germanic culture for France and England in particular.
Romano-Germanic cultural contact begins as early as our first accounts of Germanic peoples. Roman influence is perceptible beyond the boundaries of the empire, in the Northern European Roman Iron Age of the first centuries AD. The nature of this cultural contact changes with the decline of the Roman Empire and the beginning Migration period in the wake of the crisis of the third century: the "barbarian" peoples of Germania Magna formerly known as mercenaries and traders now came as invaders and eventually as a new ruling elite, even in Italy itself, beginning with Odoacer's rise to the rank of Dux Italiae in 476 AD.
The cultural syncretism was most pronounced in Francia. In West Francia, the nucleus of what was to become France, the Frankish language was eventually extinct, but not without leaving significant traces in the emerging Romance language. In East Francia on the other hand, the nucleus of what was to become the kingdom of Germany and ultimately German-speaking Europe, the syncretism was less pronounced since only its southernmost portion had ever been part of the Roman Empire, as Germania Superior: all territories on the right hand side of the Rhine remain Germanic-speaking. Those parts of the Germanic sphere extends along the left of the Rhine, including the Swiss plateau, the Alsace, the Rhineland and Flanders, are the parts where Romano-Germanic cultural contact remains most evident.
Early Germanic law reflects the coexistence of Roman and Germanic cultures during the Migration period in applying separate laws to Roman and Germanic individuals, notably the Lex Romana Visigothorum (506), the Lex Romana Curiensis and the Lex Romana Burgundionum. The separate cultures amalgamated after Christianization, and by the Carolingian period the distinction of Roman vs. Germanic subjects had been replaced by the feudal system of the Three Estates of the Realm.
Medieval aristocracy 
With a renewed close attention to the history and literature of ancient Rome in the 12th century, the medieval aristocracy saw itself mirrored in the accounts of ancient Roman nobility. Some made doubtful claims to direct descent from Roman aristocracy.
In the 19th century German and French medievalists worried about the origins of the great medieval families. Did the great families descend from the aristocracy of the Roman Empire or from the barbarian chieftains who invaded the Roman Empire between 400 and 600? Did the families originate in the Latin or Germanic world? Both it seems. Medieval Western Europe was an amalgam of Roman and 'Barbarian' bloodlines. The cultural and genetic influence of the Visigoths, Franks, et al. is readily apparent in the socio-cultural and political framework of Medieval Europe and in the Germanic physiological features of Italians of Lombardy (Lombards), the Dutch (Salian Franks) and even the English (Angles, Saxons, Jutes), to name a few. In spite of this the legacy of Rome, both social-cultural and genetic pervaded every aspect of Medieval society - this was of course greatly assisted by the medieval Church.
Beginning in the 19th century scholars such as Nikolay Yakovlevich Danilevsky and other pan-Slavism and Slavophile writers have used the term to distinguish eastern and western Europe, or Slavic-Russian culture as oppose to Romano-Germanic culture. The earliest mentions of these ideas arose when the Hellenic Byzantine east made attempts to distinguish itself from the Latin west during the times of the Roman Empire.
See also 
- Norman Cantor: The Last Knight - p.g, 10-11, 39-40
- Dennis Sherman, Joyce Salisbury: The West in the World - p.g 184