What did Rose say? Just because it's coming from an official source doesn't mean that it is comprehensive and covers everything about your application.
That being said, you'll need to figure out why they have concerns. It's tough, no doubt, and if (as many applicants tend to worry about) you think the answer is something like 'my profile is too common among Chinese applicants' then there is really nothing you can do, is there?
It is also rarely 'I'm not sure about their commitment' (which many tend to try to address by writing letters promising they'll go, or even visiting from China. All this shows commitment, but that's almost never what they're concerned about).
Finally, it is usually almost never 'this guy's GMAT is too low'- particularly if you have good undergraduate scores (and went to a relatively good school) to back you up.
Instead, it is typically 'I'm not too sure this person has thought out her career goals clearly'. Or, particularly for Chicago, 'when I read this essay I'm not too sure that the applicant has applied the analytical and methodological rigour that Chicago graduates are known for'. It could also be a whole host of other reasons.
It is up to the successful applicant to figure out 1) what is the actual reason and 2) how to deal with this. 9 out of 10 times, the things that people do (submit new gmat, show commitment, etc) do nothing whatsoever to address the problem. If anything, it merely goes to show them that you don't really understand what's wrong with your application- never a good thing for an applicant to display.