Recover deleted iMessages from iCloud?

If you are syncing Messages using iCloud, once they are deleted, you can't recover them. If you aren't syncing Messages using iCloud, restore them from a backup.

Restoring from a backup erases all data currently on your device. Any data newer than when the backup was made will be erased. A restore is an all or nothing restore.

Backup - Restore your device from an iCloud or iTunes backup

Although messages may be synced to iCloud, they are not visible or accessible there.