Changing Room Options after Room Creation? (Unity/Photon2)

Question

I was trying to make a room not joinable after the game has started. I checked other solutions but they seemed outdated. This is where I created the room:

RoomOptions ro;

public void OnClickCreate()
{
    if(RoomInput.text.Length > 0)
    {
        ro = new RoomOptions() { MaxPlayers = 2, BroadcastPropsChangeToAll = true, IsOpen = true, IsVisible = true };
        PhotonNetwork.CreateRoom(RoomInput.text, ro);
    }
}

This is where I would like to change my room options:

public void OnCLickPlayButton()
{
    ro.IsOpen = false
    ro.IsVisible = false;
    PhotonNetwork.LoadLevel("Game");       
}

The room joining works fine, but when a a original player, a player who joined the room before game starts, leaves then another player can join even through the game has already started. If you have a solution please tell me!