I would like to automatically (or manually) sync photos from a specific folder in my Dropbox account with my iPad's camera roll. I would prefer not to sync one at a time.
I don't believe that is a feature of Dropbox. You can sync your camera roll pictures to Dropbox, but the other way you need to download them one at a time.
There might be an IFTT recipe to do what you are looking for, but I am not 100% certain of that.