This is a scam. No one responds. There may be real ones mixed in. It's impossible to not get a single response from anyone. Those messages they want you to pay to see are broadcast sent to everyone who has signed up with this app. When there are this many of the same reviews, it's true.
I am sorry to learn that you are disappointed with our service but tens of thousands of our users have rented or rented out places via Roomster. I guess you are referring to our megaphone feature by broadcast. It is one of the feature that our customer loves as it allows them to ramp up their search.