POD 58 BC
In response to southern Anglo land sending Men and supplies to Help their revolting Brittany brethren, Caesar, Governor of Gaul invades across the Channel with 2 legions.
by the time He leaves for Rome in 54 BC [OTL] to shore up his Political problems, Rome controls most of south coastal England from Cornwall to Norwich.
By 10 BC Rome has been pulled North by multiple Campaigns till it controls the entire Island of Britannia. As it expands along the Eastern North Sea shore of Britannia, it also expands along the Frisian Side of the North Sea.
In 9 AD Rome sends 3 roman Legions across the Rhine to put down several tribes the have revolted against Roman Control. Accompanying the 3 Legions is a 4 legion composed of British and Frisian Foderiti.
Unlike the Romans in their Uniforms, and unused to the North Sea weather, the Foderiti are prepared for the Weather, and are in Fur Tunics with Long Kilts and Trous.
Due to the Foderiti the German Ambush is a dismal Failure, and Rome continues it's advance into Germania, eventually reaching the Elbe, where It stops, believing that there is nothing of value past the river.
By 100 AD Rome has taken the Western Shore of the Black Sea along the Danube, and begun pushing east from the north shore of Anatolia.
This increased activity causes more roman intrest in the Crimea and the Sea of Azoz.
Explorations up the Don and down the Volga, allows elements of the Roman Navy/Marines to Portage into the Caspian.
Able to Hit the Sassanids both from the North and from the East, Allows Rome to take and Hold Mesopotamia.
Having Mesopotamia, gets Rome involved in the Sassanid's attempt to take Arabia, and Rome ends up with Green and Fruitful Yemen. To control Yemen Rome establishes outposts and Fortifications along the Red Sea.
With good relations with the Axumites Rome sets a Southern Border on the Western Shore in Nubia.
by the 4th Century when the Volkswandertung begins, Rome has had two Centuries to establish it'self in the Expanded borders.