Photon Pun 2, How to have all players using the same random generation than the host's?

Okay, so I am new in Photon, and in Unity. I have followed a few tutorials here and there to build what i have right now. I have managed to create a room, to make another player see the room. When the first player create a game, the program generates a random 2D map with planets of different sizes. The problem is, when the second player joins the room, he generates it's own random map and doesn't use the one of the first player. Here are the two files that I think have an error.

CreateRoom.cs :

 using UnityEngine;
 using Photon.Pun;
 using Photon.Realtime;
 using UnityEngine.UI;
 using UnityEngine.SceneManagement;
 
 public class CreateRoom : MonoBehaviourPunCallbacks
 {
     [SerializeField]
     private Text roomName;
 
     [SerializeField]
     private int maxPlayer = 5;
 
     private RoomOptions roomOptions = new RoomOptions();
 
     public void OnClick_CreatePhotonRoom()
     { 
         if (!PhotonNetwork.IsConnected)
         {
             Debug.Log("You're not connected to the server! Connect to the server before trying to create a room");
             return;
         }
         else
         {
             roomOptions.MaxPlayers = (byte) maxPlayer;
             //roomOptions.EmptyRoomTtl = 15000;
             if(roomName.text != null)
             {
                 PhotonNetwork.CreateRoom(roomName.text, roomOptions, TypedLobby.Default);
             }
             else
             {
                 Debug.LogError("You have to specify a room name before creating a room duh");
             }
         }
     }
     
     public override void OnCreatedRoom()
     {
         Debug.Log("Room " + roomName.text + " successfully created.");
         PhotonNetwork.JoinRoom(roomName.text);
     }
 
     public override void OnCreateRoomFailed(short returnCode, string message)
     {
         Debug.Log("Failed to create the room" + roomName.text + ", cause : " + message.ToString());
     }
 
     public override void OnJoinedRoom()
     {
         Debug.Log("Room " + roomName.text + " successfully joined! :D");
         if(PhotonNetwork.IsMasterClient)
 {
             PhotonNetwork.LoadLevel("InGame");
         }
     }
 
     public override void OnJoinRoomFailed(short returnCode, string message)
     {
         Debug.Log("Failed to join the room" + roomName.text + ", cause : " + message.ToString());
     }
     
 }
 

The second one is a button on an image which when clicked, join the room of the first player :

 using Photon.Pun;
 using Photon.Realtime;
 using UnityEngine;
 using TMPro;
 public class ListingPrefab : MonoBehaviourPunCallbacks
 {
     [SerializeField]
     private TextMeshProUGUI text;
 
     public RoomInfo roomInfo { get; private set; }
 
     public void SetRoomInfo(RoomInfo roomInfo)
     {
         this.roomInfo = roomInfo;
         text.text = roomInfo.Name + " Max players : " + roomInfo.MaxPlayers;
     }
 
     public void OnClick_JoinRoom()
     {
         Debug.Log(roomInfo.Name);
         PhotonNetwork.JoinRoom(roomInfo.Name.ToString());
     }
 
     public override void OnJoinedRoom()
     {
         Debug.Log("We are connected to the room : " + roomInfo.Name);
         PhotonNetwork.LoadLevel("InGame");
     }
 
     public override void OnJoinRoomFailed(short returnCode, string message)
     {
         Debug.Log("Failed entering the room : " + roomInfo.Name + " for cause : " + message);
     }
 }

Thanks for any help :)