If the WiFi is open, there should be no need to enter anything. Even a room number. You should just be able to connect to it. Unless the place you are staying has some limitation on it. The input screen should only come up if a log in is needed.
When you tap "Settings", then "WiFi" and then tap the WiFi connection you are trying to use, what screen do you get exactly? If you can attach an image to this thread that would be helpful.