Starting today and until next Thursday, you can download the Rose prisoner avatar for Battleblock Theater for free.

As long as you've got the full version of the game and are signed into Xbox Live, once you boot up the game, Rose should be available. Here's a poem developer Behemoth wrote about Rose:

While most roses are red, some have arms and legs too, don’t mess with this one or you’ll be black and blue!

[Source: The Behemoth]