I’ve stayed at Il Bargellino several times and really like it. They have 3 rooms with direct access to a large shared terrace, 2 with private bath and 1 with shared bath as I recall. The terrace rooms are pretty quiet at night, although there’s sometimes a little bit of evening noise from others using the terrace. While the location is away from the center, walks aren’t terribly long. For example (and depending on how fast you walk), the train station and Central Market are about 5-10 minutes away, the Duomo and Accademia around 10-15 minutes, and the Uffizi and Ponte Vecchio maybe 15-20 minutes. Note that they don’t serve breakfast, but some rooms have a coffee machine (similar to a Kuerig).
I stayed at B&B Il Bargello about 5 years ago. It’s a block from the Bargello museum, so more central. It’s on the top floor, which I believe is the fifth floor, so lots of stairs. There’s a small terrace on the roof (picture on their website), which is accessed by a spiral staircase. None of the rooms have direct access to the terrace.