You have that exactly backwards. Justice Roberts redefined the Democrats' penalty/fee (which is what the rats had been proclaiming it as) into a "tax"... which was the only way it could have been deemed legal or constitutional. He rewrote the law, essentially, with his god-like ruling.
Even then, he screwed up. The penalty clause was added by the Senate, and Revenue measures (aka: taxes) are Constitutionally required to originate in the House.
He trashed the Constitution twice to rule that the ACA was acceptable, and imho, lost all credibility as a jurist..