It's not certain if and when Rooms will make it to the US, UK and other countries. The Australian and Canadian launches are really about giving Facebook a way to test English-language features with a smaller audience, to make sure they work smoothly and gauge demand for a wider rollout. However, Facebook's public announcement of Rooms suggests that you could see the feature in other regions relatively soon. As it stands, this is a safer investment than the Rooms stand-alone app. Facebook doesn't have to pour as many resources into this as it would dedicated software, and you're more likely to use the feature if it's inside an app you already use.