I am receiving conflicting information. Most seem to say the Baths are free, yet they appeared to be included in the ticket for the National Museum. Was some type of virtual reality added that might require the fee?
Ellen, I think the confusion is because of the vast amount of space the baths originally covered. The part incorporated into the National Museum of Rome does require a ticket. The part which was incorporated into the church of Santa Maria degli Angeli e dei Martiri is free.
https://www.turismoroma.it/en/places/basilica-santa-maria-degli-angeli-e-dei-martiri
https://en.wikipedia.org/wiki/Santa_Maria_degli_Angeli_e_dei_Martiri