Sometimes I have dreams in which I am a travelling dude who simply goes from city to city talking to Romans or crossing the Alps and going into Gauls/Franks territories and chatting with them. I really love those dreams. I wish could have a time-travel machine and do just that.
hi! there's lots of room for more contributions on this, but meanwhile, check out these previous related discussions
Ancient Rome: How could a foreigner make ends meet if they suddenly found themselves in Rome?
FAQ section Proof of Identity - look for posts tagged "Rome"; they're roughly in chronological order. This doesn't directly address your question, but may give some extra context on the the traveler's problem of establishing his/her identity in a foreign land
and just for fun, I can't resist including this classic from earlier this week :) Roman citizens were free to travel throughout the Empire unimpeded, but how did they prove they were Roman? Did they have the equivalent of a passport?