I think your count is somewhat off.
Is it “staunch(ly) conservative” to vote for maintaining MFN status with Red China, and to normalize trade with Vietnam? How about the statist move of countenancing “fast track” presidential trade authority? How about the extension of the “roving” warrantless wiretaps that the NSA was fond of abusing (a 2011 vote)? How about his pro-subsidy stance on agriculture? Never mind voting yes to confirm John Roberts? Furthermore, there is his liberal stances with respect to Iraq during the war, much of which have been debunked by ISIS/ISIL.
Some of the big votes that are staunchly liberal cannot have their impact measured by percentage of raw votes on the perceived conservative side.
No, my count is correct. Roberts cast hundreds of votes each year. 90% of them are conservative, and you can check his ratings from various issue groups across the board to confirm that. 10% of his votes are not conservative, so he is going to vote the "wrong" way on dozens of bills each year. Compared to Republican Senators as a whole, he has one of the most conservative voting records and is far more conservative than the average Senator. Most conservatives in America are stuck with much worst Senators and would kill for a Senator like Roberts.
Obviously, his voting record is not perfect and there are numerous votes he has cast that I do not agree with. If you want perfect, run Jesus Christ for the Senate. In the meanwhile, I will take Roberts proven 90% conservative record over a guy whose only claim to fame is that he's distantly related to the marxist-in-chief.