Hogan and Hartson has over 500 partners. Hogan and Hartson is so big that they have a pro bono group within the law firm.
It is the law firm of Hogan and Hartson and a consensus of the 500+ partners in that firm who decide what Pro Bono work is done by the firm.
The then-head of the pro bono group of Hogan and Hartson asked Roberts with all of his appellate experience to review the filings. Roberts obliged. There are many possible reasons why Roberts did so including the reason of loyalty to the law firm that he worked for.
The title of this article is misleading. All to many on this thread are all to eager to be mislead.
I agree that there are many reasons he agreed to help on the case. I also believe that an appointment to SCOTUS is something we cannot afford to screw up. That is why appointing someone who seems to have deliberately left an ambiguous paper trail is so risky. Once a Justice has voted to uphold Roe, it's a little late to say "Oops, sorry."
Why not appoint a conservative jurist who had proved his or her self? When the issue is important to Bush (CAFTA, prescription drugs or No Child Left Behind) he pulls no punches. Why not on judges?