At the beginning of the study period, all of Switzerland and Austria were parts of the Roman Empire. All of Germany west of the Rhine and the southwestern corner of Germany between the Rhine and Danube (roughly the southwestern half of modern Baden-Württemburg) were ruled by Rome. The Rhine region was an area of intense commerce and human movement. Switzerland and Austria, although backwaters, also saw their share of movement. So, if your ancestors were in these regions in 500 CE, their ancestors could have been anywhere in the Roman Empire in 1 CE.
The fifth century: Although we think of this as the great era of Germanic migrations, Germany, itself, wasn't so drastically effected by these, being a net donor of population. But something prompted the Germans to pull up stakes during this interval that effects us - the European incursions of the Huns, who originated in Mongolia (Indeed, the word "hun" is Mongolian for "person"). The Huns were the first of three important nationalities to emerge from Asia in the 4th century, conquered and ruled the Ukraine for a century, then moved into central and western Europe, where, for a few decades, they were a major power. By the sixth century, they had assimilated and ceased to exist as a nation but their genetic heritage lives on in the form of a central European cranial morphotype that is intermediate between that of East Asians and other people. (Merck represents this type. Holtz doesn't)
The Huns were followed by two other semi-nomadic central Asian nations:
Thus, If your head is uncharacteristically broad and short for a European, you may have Hunnish, Avar, or Magyar ancestry. That would place at least some of your ancestors in Central Asia, the southeast Urals, or Mongolia in 1 CE.
Eastern Germany: At the beginning of the study period, Eastern Germany was not yet ethnically German. Instead it was Baltic. Two sets of Germanic incursions to this region are significant:
During the Renaissance, Austria became the nucleus of the cosmopolitan Hapsburg Empire (Later called Austria-Hungary) which included the modern Czech Republic, Slovakia, Slovenia, Hungary, Croatia, and bits of Italy. If your ancestors lived in this region in 1800 CE, their ancestors could have come from anywhere in this Empire in 1490 CE.
One odd bit: During the 18th century, the Ottomans made their second attempt to capture Vienna. It failed and their army disintegrated. Some Austrian place names and family names suggest that remnants of the Turkish army settled there. Tom Holtz apparently stems from such ancestors.
Like France, Germany has seen its share of invading Armies, but these have not made a huge demographic impact.