Here's the information on the TMC surface: http://www.atptennis.com/en/common/...05ITW/ITW13.pdf
Unfortunately the tournament information on the ATP site still says outdoor hardcourt, and that's probably because it hasn't been updated from last year yet.
Someone on another site spoke with Greg Sharko in Cincy last week to confirm whether the roof would be open, and reported that Greg "wasn't 100% sure, but he was fairly sure the roof will remain closed during the whole event. They don't want the elements to impact the artificial carpet too much."
So it looks like it's going to be carpet, indoors.