In this post on A. Andrew Das' Paul and the Jews, I will focus on Das' interaction with Romans 14.
Das believes that Paul's audience in Romans is "almost exclusively Gentile" (page 66), for there are places in his letter where Paul addresses his audience as if it's Gentile (e.g., 1:13). Moreover, while Paul says "you Gentiles" in Romans 11:13, he never says "you Jews", and Das interprets Romans 2:17-29 to be a rhetorical address conforming to ancient diatribe, not an actual address to Jewish Christians in Paul's audience. When Paul refers to Abraham as our forefather according to the flesh in Romans 4:1, Das holds that this means Gentile Christians' status as Abraham's seed, and that it does not point to Jewish Christians in Rome who were physically descended from Abraham. Das does think, however, that Paul's Gentile audience has been influenced by Judaism in Rome, for Paul is obviously able to talk with it about such issues as the law, circumcision, and Israel, and Paul also acknowledges that it knows the law in Romans 7:1 and 15:4. But the audience, for Das, is still "almost exclusively Gentile", and the people in Romans 14 who want to observe certain days and dietary practices are Gentile God-fearers who believe in Christ and have adopted Jewish customs, not Jewish Christians. Das argues that these Gentile God-fearers were in a position unlike that of most Jews, who were able to obtain kosher items from within the Jewish community. According to Das, as Judaism and the Christ movement distanced themselves from each other, Gentile Christians who practiced Jewish customs had "difficulty obtaining the necessary kosher food items" (page 69), and so they abstained from meat and wine altogether, rather than consuming meat and wine that had been sacrificed to a pagan deity. For Das, these are the weak in faith of Romans 14.
But Das discusses another view on Romans, that of Mark Nanos. According to Das, Nanos believes that the weak in faith in Romans 14 is the broader Jewish community, and that Paul is writing to Christians who are part of the synagogue. When Paul in Romans 11 says that he hopes to make the Jews jealous by converting Gentiles, Nanos (in Das' telling) thinks that means that the Jews in the synagogue will be jealous of Paul as he brings more and more Gentiles into the synagogue. And Nanos interprets Romans 13 to concern Christian obedience to the synagogal authorities. Das notes that Nanos' book won the 1996 National Jewish Book Award in the field of Jewish-Christian relations, but Das is not convinced by Nanos' arguments. Das does not think that Paul would call non-Christian Jews weak in faith, for Paul's point in Romans 11 is that non-Christian Jews are in a state of non-belief, not weak faith. Moreover, Das asks where Paul's letter would have been read, if not a church. Against Nanos' argument that there were no churches in Rome because of an official ban on unapproved religious associations, meaning that Christians had to be part of synagogues, which were approved, Das expresses doubt that the Romans rigorously enforced that ban, plus he notes that there were places where Christians assembled apart from synagogues, such as Thessalonica, so that could have been the case in Rome, as well. Nanos sounds like Lloyd Gaston: I may not be convinced by everything he says, but I would like to read him, because I enjoy alternative interpretations of the Bible.