Can I retrieve photos on Camera roll that were deleted on my mini

That depends.

If you have enabled iCloud backups, then your camera roll will be saved to the device backup and the latest backup before you deleted from the Camera roll, may still be holding the photo:

iCloud: Backup and restore overview

Or, if you have enabled Photo stream, the Photostream may still be holding the deleted image:

iCloud: Photo Stream FAQ

Regards

Léonie

No, I don't know any way of looking into the backup. The only way to see it, is to restore:

See these two articles:

HT5125 Re: How to recover deleted photos on iCloud?

http://oberhaus-iphone.blogspot.de/2011/10/using-icloud-to-restore-accidentally. html

However, if you did not backup them to iTunes with the iPhone data recovery, you can also recover them, but the process may be a little complicated. And if you have backup the photos before, it is much easier. With this data recovery for iPhone--- iPubsoft iPhone Backup Extractor, you can extract the photos from your iTunes backup files selectively. No need to connect you iPhone to computer, therefore, even you iPhone is broken or stolen, you can recover deleted photos.

http://support.apple.com/kb/HT4083?viewlocale=en_US

There's an app that I found that can search thru the local iPhone backups via iTunes and restore selected photos to the Desktop: iBackup Viewer, the free version. If your backups are encrypted then you'll have to purchase the full version.

If they were photo stream photos, they can't be recovered. If they were camera roll photos you can recover them by restoring to your most recent iCloud backup, assuming the photos were on your iPad when the backup was created.

If you want to restore to your backup, this has to be done in the initial setup process. If you have any data on your phone now that is not in the backup that you want to save you'll need to do that first. Then go to Settings>General>Reset and tap Erase All Content and Settings. You will then go through the setup screens as you did when the phone was new. When given the option, choose Restore from iCloud Backup (see image below). Be sure you are connected to wifi and your charger as this will take some time to finish.