You can use Closure Callback or NotificationCenter
By NotificationCenter:
in DetailsViewController
func clickButtonToReloadData(){
    NotificationCenter.default.post(name: Notification.Name("ReloadDataOfTableView"), object: nil, userInfo: [:])
}
in RootViewController:
override func viewDidLoad() {
   super.viewDidLoad() 
   NotificationCenter.default.addObserver(self, selector: #selector(reloadDataOfTableView), name: "ReloadDataOfTableView", object: nil)
}
    
@objc func reloadDataOfTableView(notification : NSNotification){
    self.tableView.reloadData()
}
    
override func viewWillDisappear(_ animated: Bool) {         
    NotificationCenter.default.removeObserver(self, name: "ReloadDataOfTableView", object: nil)   
}