I was just in the St. Regis Rome last week on points, got the Imperial Double upgrade. The front desk manager escorted me to the room and showed me around, made sure I was pleased with the room. It was certainly large room with a separate sitting area. He did not mention butler service or call button, but when I called for ice, the knock on the door came quickly and someone deliver the ice bucket that certainly dressed like a butler.
Overall service was great, I asked for fruits as the amenities, and it was replenished everyday, and the quality was the best, fresh sweet and juicy!
Although it is not as close to the major attractions as I would like, about 15 minute walk to Spanish Steps/Trevi Fountain, the subway station is only one block away.