I propose that Roberts was never conservative. He was appointed by Bush, when Renquest died he was nominated for Chief Justice role before he spent a single day on the court because BOTH parties found him acceptable to not only confirm as a justice but to go straight into the Chief Justice chair.
The dems loved him, the RINOs loved him. He was never a Scalia or a Thomas, more of a Kennedy. From day one.
I agree with you that his nomination as the Chief Justice before serving a day on the SCOTUS made me wonder back then. I understand both Bushes and Yeb! much better than I did before Trump came along.
The thing is, I believe he is still compromised by that adoption.