I might be able to help a little. If this has been posted before, feel free to ignore.
1. Export your address book/contacts to CVS from your favorite email client.
2. Open the CVS file in excel (open office for the foss folks) and remove all columns that contains no data. Save the file back as CVS.
3. Open the CVS file in a text editor (notepad for windows folks) and copy the contents on to your clipboard.
4. Paste in to this apple website CSV to vCard (http://homepage.mac.com/phrogz/CSV2vCard_v2.html)
Follow the instructions.
5. This will leave you with a shiny new VCF file that you can use to import into round cube.