Photoshop Touch does not support opening camera raw images currently. The maximum image resolution is 1600x1600 with up to 16 layers. The hardware capabilities of tablet devices still has a ways to go to be able to handle this type of editing for larger images. For quick editing (like global type adjustments, like you can perform in Adobe Camera Raw or Lightroom) I know RAW support is something on the roadmap for another app, Adobe Revel. See this blog post for more info
Thats not to say it won't or couldn't be available for Photoshop Touch eventually but I wondered if Adobe Revel might be a better fit for what you're looking for (even though its not availabe yet there either).