J. Stott, The Message of Romans (IVP) - Concise and informative, very helpful on purpose and structure, great introductory commentary with that little bit more meat.
F. F. Bruce, Romans (Tyndale, No. 6) - Don't do it. He has some helpful things to say, but often ignores whole verses or misses key systematic issues. Much more helpful on introductory issues. Not one of his best.
M. Luther, Romans (Kregel Classics) - Strange little book (being only 223 pages long), more of a pulling together of various thoughts and materials than a working commentary. Yet is a surprisingly helpful and edifying read. Luther does tend to go a little overboard at times, and again skips comment on some verses.
N.T. Wright, Paul for Everyone - Again, not brilliant, sometimes helpful on breaking down a passage, but often misses verses, it seems, to fit his theological agenda. Wright is a fine exegete, but certainly not at his best here.
N.T. Wright & S. K. Soderlund (eds.) Romans and the People of God - Very helpful collection of essays in honour of Gorden Fee. These essays cover ground all over Romans and its modern application, some of them much better than others, has proved to be very insightful. Authors include, Wright, Packer, Marshall, France, Longenecker, Dunn, et al.
J. Dunn, Romans (Word Biblical Commentary, 2 Vols.) - Dunn gives us an exceptionally detailed and thoughtful piece of work, often helpful, full of detailed text work, however it does seem quite strongly that Saunders is too often drifting through the pages.
C. Cranfield Romans (T & T Clark, ICC, 2 Vols.)- Brilliant 2 volume commentary, very helpful exegetical work, very very dense. I would strongly recommend his abridged version as a way into this not particularly accessible work. N.b. Although I don't always agree with what Cranfield concludes, his text work allows the reader to use what he says and form his own opinion. I.e. The exegesis is not as pressupossionally drawn as some authors.
J. Calvin, Romans - Very helpful in parts, amazingly clear text work for such an ancient commentary, fun read (not always for the reasons Calvin would have appreciated), but conclusions often driven by a theological agenda. Though still competes with contemporary commentaries.
D. Moo, The Epistle to the Romans (NICNT) - Probably the most comprehensive and clear commentary currently on the market, very helpful, well structured, and engages multilaterally with the key issues. Moo also deals quite extensively with the New Perspective(s) on Paul.
J. Philip The Power of God - Fantastic introductory commentary, lots of fresh insight, v-helpful!