google.maps.event.addListener(marker, 'click', function() {
    $.ajax({
      type: "GET",
      url: "rooms/address_rooms",
      dataType: "json",
      data: {marker: { lat: marker.position.lat, lng: marker.position.lng }},
      success: function(result){
        $("#address_rooms").html(result);
        $('#myModal').modal('show');
      }
    });
  });

<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">
  <div class="modal-dialog modal-lg" role="document">
    <div class="modal-content">
      <div class="modal-body" id="address_rooms">
        <%- @address_rooms.each do |room| %>
          <%= room.title %>
        <% end %>
      </div>
    </div>
  </div>
</div>

def address_rooms
    marker = params[:marker]
    @address_rooms = Room.where(latitude: marker[:lat].to_d.round(7), longitude: marker[:lng].to_d.round(7)).to_a
    render json: @address_rooms
  end