Doug Moo is one of the foremost scholars on the book of Romans. His commentary on Romans in the NICNT is arguably the best ever written. If you have a question on Romans, Moo usually has the right answer and gives a fair representation of the other positions as well.
BiblicalTraining.org is offering free streaming and downloads of a D.Min. seminar Moo taught on Romans this past May at the Carolina School of Divinity.
If you want an in-depth (doctoral level) study of Romans, here you go. Best of all, it’s free.