I'm sure Justice Roberts was pressured by the other justices, and I'm sure he seriously considered reaching different decisions at different times. I'm equally sure that he decided for himself ; that he knows that each decision he writes will go down in history with him; and that even if you could speak to him privately behind closed doors, he would stand by the decision he eventually authored.
Whether you or I agree with him is a separate question, but I cannot imagine what would cause a justice to author an opinion he did not believe.