Root Double merchandise will go on sale at the next Comiket, such as:
Cushions:
http://www.yetigame.jp/w/comi80/001.html
Bags:
http://www.yetigame.jp/w/comi80/003.html
Cans (which I can't get a picture of).
They're also selling merchandise for a game called "Secret Game: Killer Queen". Never heard of it before.