A class for P.U.N (Photon Unity Networking). This class will look for an available room which is useful if you want to check room properties in advance.

RoomSelectionHelper.cs

using UnityEngine;
using System.Collections;

public class RoomSelectionHelper : MonoBehaviour {

	public bool onMasterServer = false;
	public bool inTheLobby = false;
	public int roomCount = 0;
	public int selectedIndex = -1;

	void Start(){ PhotonNetwork.ConnectUsingSettings("v4.2"); }

	void OnConnectedToMaster(){ 
		onMasterServer = true;
		PhotonNetwork.JoinLobby ();
	}

	// You could select a room here but it should be safer
	// To keep checking since room state change over time.
	void OnJoinedLobby(){ inTheLobby = true; }

	void Update(){
		inTheLobby = PhotonNetwork.insideLobby;
		if (inTheLobby) SelectRoom ();
	}

	void SelectRoom(){ 
		RoomInfo[] rooms = PhotonNetwork.GetRoomList ();
		roomCount = rooms.Length;
		foreach (RoomInfo room in rooms) {
			if (room.playerCount > 0 && room.open) { 
				if (room.playerCount < room.maxPlayers || room.maxPlayers == 0) {
					DoSelectRoom (room.name);
				}
			}
		}
	}

	// This part is custom. In our case we parse 
	// the room name to extract the level index.
	void DoSelectRoom(string name){
		int i = name.IndexOf('-');
		string indexString = name.Substring (i + 1);
		selectedIndex = int.Parse (indexString);
		GetComponent<MainMenuActions> ().survivalLevelIndex = selectedIndex;
	}
	
}