|The Via Sacra in Rome|
Question #1: Why are these roads so rough?
While some weathering has certainly occurred over the centuries to round off these stones, I doubt that they could have changed all that much. The roads paved over in large blocks of basalt in the city of Rome are very similar, if not identical, to those which have been unearhted in Pompeii over the past few centuries. I think that it is possible or even probable that sand, gravel, concrete, or other aggregate was certainly added to fill in the gaps betrween the stones, level off the surface, and create a smooth pavement. This filler would certainly have been weathered away on the exposed, paved roads of Rome and the Appian Way. Also, any loose surface material could have been innocently swept away when the streets of Pompeii were being excavated. As archaeologists in Pompeii continue to make their way down a buried street, perhaps they should pause as they get down to the paving stones and see whether something besides ash or volcanic debris can be found on the surface.
My only concern with the use of sand or dirt as a "smoothing agent" is that they would be easily washed away by the rain or waste water which would flow through the thoroughfares.