First off open up the group you want to check the room stats on by going to the groups tab on your home screen and clicking on the group.
Once open press and hold the groups name, once released it will open the group's profile, A simple click on where its stats will move you to the stats tab as shown below.
You will then get the stats of the room like the category the room is classed under, premium or not, the 14 day trend of chat activity as well as the most active users.