C# Unity - Roguelike room generation HELP

Hello :) I am fiddling arround in Unity in my freetime. I am learning by creating a roguelike. I am pretty new to the Unity Engine. Heres my problem I dont really understand: I instnatiate prefabs and it works well. But the position of each is a bit "off". Looks like a grid and not like a continous room. Heres my code I use to create this:

 void Start () {
 
         int roomWidth = rnd.Next(7, 14);
         int roomHeight = rnd.Next(10, 16);
 
         lastRoomHeight = roomHeight;
         lastRoomWidth = roomWidth;
 
 
         for(int y = 0; y < roomHeight; y ++)
         {
             for(int x = 0; x < roomWidth; x++)
             {
                 GameObject newWall = null;
                 if (x == 0 || x == roomWidth - 1 || y == 0 || y == roomHeight - 1)
                 {
                     if(x == 0 && y == 0 || x == roomWidth-1 && y == 0 || x == 0 && y == roomHeight-1 || x == roomWidth-1 && y == roomHeight-1)
                     {
                         newWall = Instantiate(floorTile, new Vector3(x, 1, y), Quaternion.identity);
                     }
                     else
                     {
                         newWall = Instantiate(wallTile, new Vector3(x, 1, y), Quaternion.identity);
                         newWall.transform.parent = this.transform;
 
                         if (y == roomHeight - 1)
                             newWall.transform.Rotate(new Vector3(0, 180, 0));
                         if (x == 0)
                             newWall.transform.Rotate(new Vector3(0, -270, 0));
                         if (x == roomWidth - 1)
                             newWall.transform.Rotate(new Vector3(0, 270, 0));
                     }
                     
                 }
                 GameObject newTile =  Instantiate(floorTile, new Vector3(x, 0, y), Quaternion.identity);
                 newTile.transform.parent = this.transform;
             }
         }

Maybe someone can see what I am doing wrong. I appreciate any help I can get :)