Here's what Trippy members say about National Roman Museum - Baths of Diocletian:
"Assuming that you start from Stazione Roma Termini you will walk around the ancient roman city, starting from National Roman Museum - Baths of Diocletian (it will take some hours to visit it) then walk (about 30 minutes) to Colle Palatino, Colosseo, Circo Massimo, and the Bocca della Verità where you will spend the rest of the day." See More