Adam Clarke on Romans 16:21

Timotheus my workfellow - This is on all hands allowed to be the same Timothy to whom St. Paul directs the two epistles which are still extant. See some account of him in the notes on Act 16:1 (note), etc.

Lucius - This was probably Luke the evangelist, and writer of the book called The Acts of the Apostles. For a short account of him see the Preface to that book.

Jason - It is likely that this is the same person mentioned Act 17:7, who at Thessalonica received the apostles into his house, and befriended them at the risk both of his property and life.

Sosipater - He was a Berean, the son of one Pyrrhus, a Jew, by birth, and accompanied St. Paul from Greece into Asia, and probably into Judea. See Act 20:4.