I sincerely hope that C profited from the above suggestions. Just for the record, I'd like to apologize for a blunder in my post #6. "The role of X in Y" is standard, the "role of X for Y" may be possible in certain contexts. I was mislead by a huge amount of Goo-hits for the latter. Initially, I had written "the role for may be possible, but I'm not sure", and I now see that my instinct was right. I checked some of the 130 millions of hits for "the role+for", limiting my interest to research papers, and I found that all of those which used "the role of X for Y" were written by non-native speakers of English and/or published in non-Englishspeaking countries. I just checked the first dozen of entries, and the result was devastating. This is another example for how the English language suffers from globalization. There are, of course, many examples of correct use of 'for' with a different object (as mentioned by hm-us in #9).
Well, haste takes its tolls, but when I read the initial replies (not from the 'daddy' we know, I presume) and saw how politely and patiently C responded to these faulty and misleading suggestions, I felt I had to hurry up and invite others ...
C will probably have delivered his or her "Verteidigung" of his/her dissertation by now. In English (which I think is an outrage in itself, by the way). And including a number of mistakes such as 'in regard to' which won't have any influence on the result of the examination.
I feel I have to communicate this to all who have contributed, after the event, as it may be.