You probably have close relations with guys on the other side of the river at first, including family relations. However, the Romans realised how dangerous this was, so they tried to break up possible cross-border relations. Caesar already started this process by inviting entire groups from further away to settle in the border zone, and the Julio-Claudian emperors also employed an active policy of depopulation of the immediate cross-Rhine frontier (at least removing population that were not sanctioned to live there by the Romans, and sometimes allowing settlement by dissident communities under Roman protection). Other than that, in terms of lifestyle there would be minimal differences. The Romans, particularly in the first decades, did not integrate local communities that much into imperial economies, including the military economy. Besides legal and political subjugation, local communities simply continued to live a native, barbarian lifestyle. Recruitment into the army happened among both foreign and domestic communities, but the communities inside the borders (particularly those 'invited' by the Romans) had an obligation to serve (and pay taxes), while those across the border did so voluntarily (and could provide either 'gifts' or be subjected to tribute). Over time, Roman hierarchies did play a greater role in communities inside the borders (with returning veterans taking up leadership roles in their native communities, and with the expansion of the villa system in Gallia), and access to Roman industrial and luxury goods is easier for communities inside the borders (if they choose), while outside the borders the Romans emphasise and sponsor the power of individual strongmen/warlords, making status differences more pronounced here as well. So over time, a German inside the borders would be subjected to Roman laws, while one outside of them to the Roman-sponsored leader.