roberts vote on one bill has not changed his votes on hudreds of others. he did not become a liberal with one vote.
Mathematically, you are correct. But the Constitutional cortorsions he went through to justify Obamacare were extraordinary and very disturbing. I would argue that this one landmark vote was so damaging to our freedom that it has set precedent which will render meaningless many FUTURE attemtps to restore our liberties. One big failure can destroy many working parts, if not the whole system.
BTW Congress should find a law or rule to eliminate with every law they pass.