If you want to save a photo from Dropbox Carousel to iPhone's camera roll, then click on the photo which you want to save. Tap the "Share" icon located at the bottom left corner on the screen and select "Save" option. Once you have saved photo, you can view it in your iPhone's camera roll. Dropbox Carousel allows you to save one photo at a time. You can also save a photo that someone shared with you. to do so, tap "Save photo to Dropbox" button located within the conversation. Now you can save photo to your iPhone directly from your own Carousel Timeline.