When drawing from a sprite, you can supply a source rectangle, to draw only a subset of it. That subset can be scaled and rotated as if it were the entire sprite. We don’t have a formal means of defining a full atlas at the moment, but as long as you know the rectangle you need from the spritemap, you can use a single image for all your animation.
Right now we are building small games to show you the API in use, but while this is nice in some ways, it’s completely annoying in others, so we’ll be writing formal documentation soon so everyone can reach for what works best for them. :)