Here's what visitors thought to be the best explanations for shifts in thought between Galatians and Romans.
72% (18 votes) -- change in audience/church situation
16% (4 votes) -- Paul struggling with theological dilemmas
12% (3 votes) -- Paul's increasingly sophistic and deceptive rhetoric
0% (0 votes) -- a bad reputation Paul had acquired since Galatians
I'm not surprised that Paul's bad reputation didn't get any votes, because an emphasis on this factor is rather new. Thomas Tobin's Paul’s Rhetoric in its Contexts has yet to make the impact it deserves. Most, not suprisingly, favor the audience factor. That includes me, though I think all four are important.
I plan on having a functional outline/commentary up soon, which will explain sections of Rom 1:18-15:13 in terms of Paul's audience in Rome, but also with an eye on his theological dilemmas, reputation, and increasingly deceptive rhetoric. All four need attention when solving the Romans puzzle.