Hi Minko,
for my trip to Sicilia I used a map from http://garmin.openstreetmap.nl/using the Openfietsmap Lite
style. I also noticed quite a lot of crashes (maybe one per day) on my Oregon 600. I did not relate that to
roundabouts but in Italy a roundabout is never far away.
Most of the time I followed a track, so I think they were not related to routes.
BUT in one case the device crashed two times within a short time, and yes, I was aproaching a roundabout and
using a route calculated by the device.
I still have the recorded gpx files and the img file for the map in case these can help you.
Gerd