The column should've extended for 10 kilometers. SOme others settled near the Headui, Rome's allies. WE have to assume more than 200.000 were either killed or enslaved. Now, to Roman times. Most of Helvetia, that is the land between Jura and Alps, were finally included in Germania Superior, Eastern part being Raetia, and canton of Valais being a main part of the small province of Alpes Graiae et Poeninae.
Some road follow quite the same path as the Roman ones indeed.
Problems came in 260 with the first invasion of the Alemanni. Other invasions came thereafter, and it isn't really sure at which time the main cities were abandoned. For instance, parts of Nyon's buildings were used to make walls around Geneva, which could mean that the former has been abandoned. Finally, Burgunds came and occupied the western half of the ladn, and Alemanni got the eastern one. Burgunds were more civilised and romanised than Alemanni, so latin was still spoken in west, but german was then used est.