1. The process of rooting your phone wipes all data; this is a necessary security precaution - otherwise anyone who found your phone could simply root it and then have access to your most precious stuff. So, for file recovery tools to work at all, you need to root your phone *before* you need it, not after.
2. Even then, recovery of deleted files is a very iffy proposition and the more you use the phone between the time you deleted files and the time you try to recover them, the less likely you are to be successful.
Sorry, but the news is not good.
On the other hand, if he set up his phone correctly, he may find that his photos were backed up to the cloud, either at photos.google.com or at Samsung's cloud which, honestly, I don't know how to access since I haven't owned a Samsung device in years.