`Roman', an exegesis on Paul's Epistle to the Romans by F. F. Bruce is an excellent mid-level commentary on this most important book of the Christian New Testament. I am reviewing a 1985 Second edition which has many notable improvements over the 1963 First Edition, especially the switch to the RSV translation and consultations with some of the most important scholarly commentaries on `Romans' such as the one done by Ernst Kasemann.
One of the few problems with Professor Bruce's edition is that it falls smack in the middle of Bible commentary styles. It is seriously scholarly, especially in it's very important interest in avoiding `political correctness' when covering some of Paul's stronger opinions possibly not too popular in today's world. On the other hand, the book belongs to a `popular' series, `The Tyundale New Testament Commentaries' and it aims at serving the lay Bible Study audience.
Since I believe that when dealing with serious and difficult subjects, it is best not to lead your audience into a false sense of simplicity, I applaud Professor Bruce's leaning in the direction of the scholarly, with battalions of footnotes, Greek and Aramaic texts, and careful expositions on central concepts such as `flesh', `spirit', and `righteousness'.
Thus, Bruce is deeper and potentially more satisfying than William Barclay's `The Letter to the Romans', which has few of these. Bruce's analysis of Paul's letter is distinctly more carefully thought out than Barclay's one-dimensional list of subjects. Oddly, Bruce diverges substantially from both Kasemann and N. T. Wright in his commentary in `The New Interpreter's Bible' in his outline of the Epistle around Chapter 3 Verse 20. In this, he follows the scholarly Kasemann's lead, so I anticipate he has important good scholarship on his side.
Aside from the scholarly (Kasemann) and the lay (Bruce, Barclay, and Wright) commentaries, one may also wish to consider the theologically based commentaries from, for example Martin Luther and John Barth. These approaches may be great for a history of ideas, but they are to be avoided as a best source of what Paul was really saying. Luther and other early Reformation leaders saw Paul as a supporter of their own agenda. But, while Luther may have been seeing Paul correctly on many points, he may also have been misreading Paul's emphasis and especially misreading him on Paul's analysis of the failure of the Jews.
My first choice for a lay commentary is Wright's monograph cited above. The only problem with that is that you need to buy the whole volume X or read it while sitting in your library's reference room stacks. On the other side of the coin, if you or your church can spring for the entire `New Interpreter's Bible', you have scholarly works on the entire scripture. And, I find Wright's text easier for aging eyes to read, and his bibliography is more current (however, I found nothing of importance missing from Bruce's bibliography).