diff --git a/backend/src/main/java/io/f1/backend/domain/game/app/GameService.java b/backend/src/main/java/io/f1/backend/domain/game/app/GameService.java
index fe2d99e2..6e74acc4 100644
--- a/backend/src/main/java/io/f1/backend/domain/game/app/GameService.java
+++ b/backend/src/main/java/io/f1/backend/domain/game/app/GameService.java
@@ -219,16 +219,9 @@ public void changeGameSetting(
         if (!request.change(room, quizService)) {
             return;
         }
-        request.afterChange(room, messageSender);
+        request.afterChange(room, messageSender, eventPublisher, quizService);
 
         broadcastGameSetting(room);
-
-        RoomUpdatedEvent roomUpdatedEvent =
-                new RoomUpdatedEvent(
-                        room,
-                        quizService.getQuizWithQuestionsById(room.getGameSetting().getQuizId()));
-
-        eventPublisher.publishEvent(roomUpdatedEvent);
     }
 
     private void validateRoomStart(Room room, UserPrincipal principal) {
diff --git a/backend/src/main/java/io/f1/backend/domain/game/app/RoomService.java b/backend/src/main/java/io/f1/backend/domain/game/app/RoomService.java
index 418dbfbe..9596159e 100644
--- a/backend/src/main/java/io/f1/backend/domain/game/app/RoomService.java
+++ b/backend/src/main/java/io/f1/backend/domain/game/app/RoomService.java
@@ -26,6 +26,7 @@
 import io.f1.backend.domain.game.dto.response.RoomSettingResponse;
 import io.f1.backend.domain.game.dto.response.SystemNoticeResponse;
 import io.f1.backend.domain.game.event.RoomCreatedEvent;
+import io.f1.backend.domain.game.event.RoomDeletedEvent;
 import io.f1.backend.domain.game.model.ConnectionState;
 import io.f1.backend.domain.game.model.GameSetting;
 import io.f1.backend.domain.game.model.Player;
@@ -349,6 +350,8 @@ private void cleanRoom(Room room, String sessionId, Player player) {
         /* 방 삭제 */
         if (room.isLastPlayer(sessionId)) {
             removeRoom(room);
+            Long roomId = room.getId();
+            eventPublisher.publishEvent(new RoomDeletedEvent(roomId));
             return;
         }
 
diff --git a/backend/src/main/java/io/f1/backend/domain/game/dto/request/GameSettingChanger.java b/backend/src/main/java/io/f1/backend/domain/game/dto/request/GameSettingChanger.java
index fa3a4981..e8b2c65f 100644
--- a/backend/src/main/java/io/f1/backend/domain/game/dto/request/GameSettingChanger.java
+++ b/backend/src/main/java/io/f1/backend/domain/game/dto/request/GameSettingChanger.java
@@ -4,9 +4,15 @@
 import io.f1.backend.domain.game.websocket.MessageSender;
 import io.f1.backend.domain.quiz.app.QuizService;
 
+import org.springframework.context.ApplicationEventPublisher;
+
 public interface GameSettingChanger {
 
     boolean change(Room room, QuizService quizService);
 
-    void afterChange(Room room, MessageSender messageSender);
+    default void afterChange(
+            Room room,
+            MessageSender messageSender,
+            ApplicationEventPublisher eventPublisher,
+            QuizService quizService) {}
 }
diff --git a/backend/src/main/java/io/f1/backend/domain/game/dto/request/QuizChangeRequest.java b/backend/src/main/java/io/f1/backend/domain/game/dto/request/QuizChangeRequest.java
index 1237a44c..cfb4e5f9 100644
--- a/backend/src/main/java/io/f1/backend/domain/game/dto/request/QuizChangeRequest.java
+++ b/backend/src/main/java/io/f1/backend/domain/game/dto/request/QuizChangeRequest.java
@@ -5,12 +5,15 @@
 
 import io.f1.backend.domain.game.dto.MessageType;
 import io.f1.backend.domain.game.dto.response.PlayerListResponse;
+import io.f1.backend.domain.game.event.RoomUpdatedEvent;
 import io.f1.backend.domain.game.model.Room;
 import io.f1.backend.domain.game.websocket.MessageSender;
 import io.f1.backend.domain.quiz.app.QuizService;
 
 import lombok.extern.slf4j.Slf4j;
 
+import org.springframework.context.ApplicationEventPublisher;
+
 @Slf4j
 public record QuizChangeRequest(long quizId) implements GameSettingChanger {
 
@@ -21,17 +24,28 @@ public boolean change(Room room, QuizService quizService) {
         }
         Long questionsCount = quizService.getQuestionsCount(quizId);
         room.changeQuiz(quizId, questionsCount.intValue());
+        room.resetAllPlayerReadyStates();
         return true;
     }
 
     @Override
-    public void afterChange(Room room, MessageSender messageSender) {
-        room.resetAllPlayerReadyStates();
+    public void afterChange(
+            Room room,
+            MessageSender messageSender,
+            ApplicationEventPublisher eventPublisher,
+            QuizService quizService) {
 
         String destination = getDestination(room.getId());
         PlayerListResponse response = toPlayerListResponse(room);
 
         log.info(response.toString());
         messageSender.sendBroadcast(destination, MessageType.PLAYER_LIST, response);
+
+        RoomUpdatedEvent roomUpdatedEvent =
+                new RoomUpdatedEvent(
+                        room,
+                        quizService.getQuizWithQuestionsById(room.getGameSetting().getQuizId()));
+
+        eventPublisher.publishEvent(roomUpdatedEvent);
     }
 }
diff --git a/backend/src/main/java/io/f1/backend/domain/game/dto/request/RoundChangeRequest.java b/backend/src/main/java/io/f1/backend/domain/game/dto/request/RoundChangeRequest.java
index b44cb72a..76244ffd 100644
--- a/backend/src/main/java/io/f1/backend/domain/game/dto/request/RoundChangeRequest.java
+++ b/backend/src/main/java/io/f1/backend/domain/game/dto/request/RoundChangeRequest.java
@@ -1,7 +1,6 @@
 package io.f1.backend.domain.game.dto.request;
 
 import io.f1.backend.domain.game.model.Room;
-import io.f1.backend.domain.game.websocket.MessageSender;
 import io.f1.backend.domain.quiz.app.QuizService;
 
 public record RoundChangeRequest(int round) implements GameSettingChanger {
@@ -17,9 +16,4 @@ public boolean change(Room room, QuizService quizService) {
         room.changeRound(round, questionsCount.intValue());
         return true;
     }
-
-    @Override
-    public void afterChange(Room room, MessageSender messageSender) {
-        // 고유한 후처리 동작 없음
-    }
 }
diff --git a/backend/src/main/java/io/f1/backend/domain/game/dto/request/TimeLimitChangeRequest.java b/backend/src/main/java/io/f1/backend/domain/game/dto/request/TimeLimitChangeRequest.java
index aa088c7d..2e58f679 100644
--- a/backend/src/main/java/io/f1/backend/domain/game/dto/request/TimeLimitChangeRequest.java
+++ b/backend/src/main/java/io/f1/backend/domain/game/dto/request/TimeLimitChangeRequest.java
@@ -1,7 +1,6 @@
 package io.f1.backend.domain.game.dto.request;
 
 import io.f1.backend.domain.game.model.Room;
-import io.f1.backend.domain.game.websocket.MessageSender;
 import io.f1.backend.domain.quiz.app.QuizService;
 
 public record TimeLimitChangeRequest(int timeLimit) implements GameSettingChanger {
@@ -14,9 +13,4 @@ public boolean change(Room room, QuizService quizService) {
         room.changeTimeLimit(TimeLimit.from(timeLimit));
         return true;
     }
-
-    @Override
-    public void afterChange(Room room, MessageSender messageSender) {
-        // 고유한 후처리 동작 없음
-    }
 }
diff --git a/backend/src/main/java/io/f1/backend/domain/game/mapper/RoomMapper.java b/backend/src/main/java/io/f1/backend/domain/game/mapper/RoomMapper.java
index cb662875..48b76ad6 100644
--- a/backend/src/main/java/io/f1/backend/domain/game/mapper/RoomMapper.java
+++ b/backend/src/main/java/io/f1/backend/domain/game/mapper/RoomMapper.java
@@ -48,6 +48,7 @@ public static RoomSettingResponse toRoomSettingResponse(Room room) {
         return new RoomSettingResponse(
                 room.getRoomSetting().roomName(),
                 room.getRoomSetting().maxUserCount(),
+                room.getCurrentUserCnt(),
                 room.getRoomSetting().locked());
     }
 
@@ -71,7 +72,7 @@ public static RoomResponse toRoomResponse(Room room, Quiz quiz) {
                 room.getId(),
                 room.getRoomSetting().roomName(),
                 room.getRoomSetting().maxUserCount(),
-                room.getPlayerSessionMap().size(),
+                room.getCurrentUserCnt(),
                 room.getRoomSetting().locked(),
                 room.getState().name(),
                 quiz.getTitle(),
@@ -111,9 +112,9 @@ public static QuestionStartResponse toQuestionStartResponse(Room room, int delay
                 room.getCurrentQuestion().getId(),
                 room.getCurrentRound(),
                 Instant.now().plusSeconds(delay),
-                room.getGameSetting().getTimeLimit(),
+                room.getTimeLimit(),
                 Instant.now(),
-                room.getGameSetting().getRound());
+                room.getRound());
     }
 
     public static GameResultResponse toGameResultResponse(
diff --git a/backend/src/main/java/io/f1/backend/domain/game/sse/mapper/SseMapper.java b/backend/src/main/java/io/f1/backend/domain/game/sse/mapper/SseMapper.java
index efdd94c8..869e0219 100644
--- a/backend/src/main/java/io/f1/backend/domain/game/sse/mapper/SseMapper.java
+++ b/backend/src/main/java/io/f1/backend/domain/game/sse/mapper/SseMapper.java
@@ -21,7 +21,7 @@ public static LobbySseEvent<RoomCreatedPayload> fromRoomCreated(RoomCreatedEvent
                         room.getId(),
                         room.getRoomSetting().roomName(),
                         room.getRoomSetting().maxUserCount(),
-                        room.getPlayerSessionMap().size(),
+                        room.getCurrentUserCnt(),
                         room.getRoomSetting().locked(),
                         room.getState().name(),
                         quiz.getTitle(),
@@ -38,7 +38,7 @@ public static LobbySseEvent<RoomUpdatedPayload> fromRoomUpdated(RoomUpdatedEvent
         RoomUpdatedPayload payload =
                 new RoomUpdatedPayload(
                         room.getId(),
-                        room.getPlayerSessionMap().size(),
+                        room.getCurrentUserCnt(),
                         room.getState().name(),
                         quiz.getTitle(),
                         quiz.getDescription(),