The people at Ave Maria University’s Aquinas Center have posted a PDF containing an English translation of Aquinas’s commentary on Romans (based upon Fr Fabian Larcher, O.P.’s translation). Jeremy Holmes did the updating and editing. As mentioned here three years ago (!), the Aquinas Center has a page on their website linking to PDFs of Aquinas’s commentaries in English on: Hebrews, 1 and 2 Corinthians, Colossians and Ephesians. The one on Romans now joins that earlier group.