The vast majority of people would never have willingly traveled far from their birthplace, in medieval Europe or the Roman Empire. This is especially true for those who had few skills. You could do basic labor in your own village, but how could you leave without any money or support network (e.g., a family)? Why would people trust you elsewhere? The dynamic was probably different in larger cities, of which there were more in Roman times compared to the (at least early) medieval period though.
This had little to do with serfdom, and practices that would fit under what we might call serfdom were extremely varied from time and place. It would have been very rare for someone to have the means, ability, and desire to move far from their home yet couldn't because they were somehow legally bound to land owned by a lord (who only had power over that one area anyhow).
The speculation is that there were created by advanced apprentices. What we’d now call “journeymen.” Most people didn’t move around maybe, but I wouldn’t be that surprised to find that they did.
They absolutely would have moved around since one of the most common ways to get the apprenticeships was to sign up to help with an army that was mobilizing for war. Militaries needed a lot of blacksmiths to tag along as support and they needed a lot of apprentices for manual labor. When they came back from, they often had a little more choice in where to go back to so they had quite a bit more mobility over all.
Not just that, but "head out with the military, stay where you end up (or somewhere along the route)" is a tried-and-true method of moving people throughout history. How else would you end up with Latin dialects spoken over a range from Portugal to the Black Sea?
People travelled, but regular people didn't routinely travel to the other side of the empire. The road network was probably used more for "local travel" than "far travel".
Sure, but for the vast majority of workers and artisans they would most likely do a pilgrimage. And we have found tons of little charms, even penises, but they are all much smaller than any of the dodecahedrons.
Travel with luggage is what I was referring to as rare for most people.
During roman period most likely people traveled for festivals.
Archaeologists have found what could be temporarily built up areas for festivals. And it is known that festivals were a big thing that gave the population a break from work.
Which is what I personally would like to connect with the famous penis pendants, but nobody knows for sure. They could just be fertility symbols related to courtship and marriage.
FYI I'm doing a lot of guessing here, which is apt when it comes to discussing dodecahedrons. In my opinion you can look at contemporary, or near contemporary, rural communities and see a lot of similarities with ancient society.
The roads were mainly for the army though. And water travel was almost always preferable when traveling long distances (the cost of shipping for goods was a magnitude or more lower).
This had little to do with serfdom, and practices that would fit under what we might call serfdom were extremely varied from time and place. It would have been very rare for someone to have the means, ability, and desire to move far from their home yet couldn't because they were somehow legally bound to land owned by a lord (who only had power over that one area anyhow).