The basemap file don't have road but we using in order to run iGO at the first time (after the downloading) without using any map.
Basemap show us the border of countrys and furthermore with basemap can see all the countrys (if you select a point in the map and then press the button
"-") with their names if we have in the folder map just one map.
Basemap is needed in some cases if you use different map for some countrys:e.x Navteq for Germany, Teleatlas for Austria, so if you try to make a trip from Germany to Austria then it might have problem with the programm when you try to set this trip. But if you use a Basemap then surely you will not get any error.
For my opinion, try to set an old one basemap.