Rovio and Nokia announced today that Angry Birds Roost will be an exclusive “companion app” for the Nokia Lumia smartphone line for the next three months.

The Windows 8 app isn’t a game. Rather, it helps you play the games. It has reviews of various Angry Birds apps, walkthroughs for detailed descriptions of how to beat the game, and other supplemental material. The app could help establish the Angry Birds brand on the Nokia platform. Right now, both parties could use the help. Nokia’s new Lumia smartphones use Windows Phone 8 and have a big battle against Apple iPhones and Google Android devices. And Angry Birds games have seen a dip in popularity recently as Rovio readies a number of new games and brand extensions.

Rovio’s next big game, Bad Piggies, launches on Sept. 27. The Angry Birds Roost app will be available on the Nokia Lumia 920 and Nokia Lumia 820. There will be hundreds of walkthrough videos, news items, ringtones and more. The app features an exclusive “Roost Cam” feature where users can take a picture on their phone, add their favorite Angry Birds characters to the picture, and then share it on Facebook, Twitter, MMS or email. The app will have lots of wallpapers and a Live Tile on the Lumia start screen (that gives it a prime position to get noticed).

“Angry Birds Roost is a fantastic place for fans,” said Peter Vesterbacka, Mighty Eagle and chief marketing officer of Rovio. “Bursting with amazing content, it’s a great way for Lumia users to get the full Angry Birds experience all in one app.”