diff --git a/package.json b/package.json
index ad5b8615..d2631839 100644
--- a/package.json
+++ b/package.json
@@ -26,8 +26,14 @@
       "default": "./dist/server.js"
     },
     "./rosocket": {
-      "import": "./dist/rosocket.js",
-      "require": "./dist/rosocket.cjs",
+      "import": {
+        "types": "./rosocket/index.d.ts",
+        "default": "./dist/rosocket.js"
+      },
+      "require": {
+        "types": "./rosocket/index.d.cts",
+        "default": "./dist/rosocket.cjs"
+      },
       "default": "./dist/rosocket.js"
     },
     "./lib/*": "./lib/*.js",
diff --git a/rosocket/index.d.cts b/rosocket/index.d.cts
new file mode 100644
index 00000000..a15c8901
--- /dev/null
+++ b/rosocket/index.d.cts
@@ -0,0 +1,20 @@
+// Copyright (c) 2026 RobotWebTools Contributors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// CommonJS type entry for `require('rclnodejs/rosocket')`.
+//
+// Re-exports the ESM declarations so the `require` condition has a CommonJS
+// (`.d.cts`) type file whose module format matches the CommonJS JavaScript
+// served by the same condition.
+export * from './index.js';
diff --git a/rosocket/index.d.ts b/rosocket/index.d.ts
new file mode 100644
index 00000000..cfcb5f38
--- /dev/null
+++ b/rosocket/index.d.ts
@@ -0,0 +1,73 @@
+// Copyright (c) 2026 RobotWebTools Contributors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Type surface for the `rclnodejs/rosocket` subpath export.
+//
+// `rosocket` exposes ROS 2 topics and services as plain WebSocket URLs that
+// carry ROS messages as JSON. Only the public `startRosocket` entry point is
+// typed here.
+
+import type { EventEmitter } from 'node:events';
+import type { IncomingMessage } from 'node:http';
+import type { Node } from 'rclnodejs';
+
+/** Options accepted by {@link startRosocket}. */
+export interface StartRosocketOptions {
+  /** rclnodejs Node to host publishers/subscriptions/clients on. */
+  node: Node;
+  /** Port to listen on. Default `9000`. */
+  port?: number;
+  /** Host to bind to. Default `'0.0.0.0'`. */
+  host?: string;
+  /**
+   * Optional default type per topic name,
+   * e.g. `{ '/chatter': 'std_msgs/msg/String' }`.
+   */
+  topicTypes?: Record<string, string>;
+  /** Optional default type per service name. */
+  serviceTypes?: Record<string, string>;
+  /**
+   * Optional auth hook called with the raw HTTP upgrade request; return
+   * `false` to reject the connection.
+   */
+  verifyClient?: (req: IncomingMessage) => boolean;
+}
+
+/** Handle returned by {@link startRosocket}. */
+export interface RosocketServer {
+  /**
+   * The underlying WebSocket server (a `ws` `WebSocketServer`, typed here as
+   * its `EventEmitter` supertype to avoid a hard dependency on `ws` types).
+   */
+  wss: EventEmitter;
+  /** Stop the gateway and close all connections. */
+  close: () => Promise<void>;
+  /** The port the gateway is listening on. */
+  port: number;
+}
+
+/**
+ * Start a resource-style WebSocket gateway that exposes ROS 2 topics and
+ * services as plain WebSocket URLs carrying ROS messages as JSON.
+ *
+ * URL scheme:
+ * - `ws://host:port/topic/<topic_name>?type=<pkg>/msg/<Type>`
+ * - `ws://host:port/service/<service_name>?type=<pkg>/srv/<Type>`
+ *
+ * @param options - Gateway configuration. `options.node` is required.
+ * @returns A Promise resolving with the gateway handle.
+ */
+export function startRosocket(
+  options: StartRosocketOptions
+): Promise<RosocketServer>;