In a recent speech, he cited Robert Jackson, Felix Frankfurter, and John Marshall Harlan (the younger) as his judicial role models. None of these justices could be described as doctrinaire conservatives. He also said that he admired William Rehnquist for his collegiality--but he also said the same about William Brennan.
http://www.phxnews.com/fullstory.php?article=23439
From reviewing what Roberts has said in the past, we do not really know what he will do in relation to abortion. This appointment is not a litmus test on abortion, homosexual rights, or anything else. The question is: will this man faithfully interpret the Constitution and Federal statutes? He has quoted Justice Felix Frankfurters instruction to his students; and Frankfurter said, Read the statute, read the statute, read the statute. Judge Roberts is going to be strong on statutory interpretation and strong on Constitutional interpretation. He is not somebody who wants to legislate from the bench. This is exactly what the President said that he would give us and he has
Unless you have something else on Roberts concerning Frankfurter, I think that hardly makes Roberts a liberal.
Even the person authoring the comment above went on to say Roberts going to be strong on constitutional interpretation.