Restore

If the app is deleted the data is also deleted. However, if you have a backup then there are other risks. Read on...

Is it iCloud backup? If you delete on iPhone it is gone from iCloud too.

iCloud backup doesn’t include information already stored in iCloud, like Contacts, Calendars, Bookmarks, Mail, Notes, Voice Memos, shared photos, iCloud Photos*, Health data, call history, and files you store in iCloud Drive.

*-If you had turned on iCloud Photos, your content is automatically stored in iCloud. 

Is it iTunes backup?

Though restore from iTunes backup is an option but you need to restore the entire iPhone (only the Photos restoration option does not exist) including all apps, Messages, Photos, Videos, Voice Memos, Notes on your iPhone etc...

The question is when did you back up on iTunes and when did you delete it...Read on...

Let us assume...

Date1 : Backup date

Date2 : Photo / Video Deletion Date

Date3 : Current Date / Restoration Date

Given that --> Date1 < Date2 < Date3 

Risk of restoring on Date3: You may lose data between the Date1 & Date 3

Mitigation: Create Multiple back-ups on iTunes for the same device. (By default iTunes creates incremental back up on the existing backup such that you only will have one backup per device on iTunes)

How to create Multiple Backup for the same device.

1. 1. On iTunes Click on Manage Backups
   2. Right Click on a Backup and Click Archive
   3. Click Backup Now.
   4. You will see a fresh backup will get created See the GIF below
   5. 
   6. Restore from Backup dated Date1 (Archived)
   7. Retrieve the Photos / Videos and store them separately
   8. Restore from Current Backup Date3