If they were saved as Google contacts and you have contact syncing enabled you should be able to just resync them (assuming you didn't just delete them individually, in which case the changes will have been synced too). You can always check by logging into your GMail account from a browser and viewing the stored contacts there (click on the little red word "GMail" and select "contacts").
Otherwise, unless they were backed up some other way there's no way of doing it.
Personally I have my contacts synced with Google and make separate backups, because I don't like to trust a single source for backups. But the important thing is to have backups.