I don't know whether to be more irritated with Apple for not providing a batch mechanism or with the app developers for restricting their input to the camera roll (unless that's an Apple requirement).
The lack of a batch mechanism is annoying, but the restriction to the Camera Roll is built deep into the saftety restriction for IOS devices. Apps are restricted to their "Sandbox", and the Camera Roll is the central sharing place for photos on iOS devices. There is no way to circumvent this.
Maybe, your problem to get the photos into the Camera Roll is due to using Dropbox and not one of Apple's own provided tools to transfer the photos, see the list of possibilities to transfer photos between devices. For example, Photo Stream would save the photos automatically to the Camera Roll. Or use iTunes Photos sync.
http://help.apple.com/iphoto/iphone/2.0/?handbuch#blnka7d353af
Once you can make iPhoto see the photos in an album, you can batch-save them to to camera roll: (http://help.apple.com/iphoto/iphone/2.0/?handbuch#blnkee26bc1f)
- Tap a photo, album, or event and tap the share button > Camera Roll.
- Tap Selected, or change the photos you want to save:
- Select different photos: Tap Choose Photos, tap up to 100 photos, and tap Next.
- Select a range of photos: Tap Choose Photos, tap Range, tap the first and last photos in the range, and tap Next.
- Select all the photos in an album or event: Tap All.
- Tap Done.
- To use your photo in another app, open the app and select the Camera Roll album.