@Roads: while "urban" roadwork would have been dissembled. Roads connecting Settlements were often built over by the romans and most people(in this case archaeologists) understandably are pretty happy with finding a roman road and would not dare to dig deeper(destroying the roman road they just found) to look for possible Celtic roads underneath. Afterall Caesar would not have marched through Gaul the way he did if they did not have roads^^.
Afaik those roads would have been made of(covered with) wood rather than stone tho.