I don't think you know what a devout Jew is. Devout means religious and a religious Jew is Orthodox, they observe all the laws, the big one being the Sabbath law. Rosen may identify strongly as a cultural ethnic Jew. I bet his family are Reform Jews, they don't believe anything, they don't believe in the God of the Old and New Testament, they say they find meaning in the Bible but none of it is divinely inspired or transmitted, a nice fairytale basically. He won't be offended by any religious speeches given by coaches or Christian teammates.
The Jewish and Christian God are the same entity anyway, religious Jews just reject that Jesus Christ was/is the Messiah.