I went with a friend and we used both rooms. We had to throw a coin, because the second bedroom has no window (and no AC) and the high temperatures during our stay did not make that inviting... Personally I am not keen on ACs anyway and I made do with the fan (from the ceiling). Those are in all rooms and surprisingly effective. The bedrooms share a wall with glass panes on top, not well insulated, which means the noise from the street (or the other room) travels nicely.
The accomodation as such is a fabulously restored 16./17.century flat in a sterling location with lovely restaurants,good bars and buses close by. Trastevere is a vibrant and beautiful quater.
We had a hiccup with the cleanness in the kitchen. The host corrected that to our fullest contentment after a second text from us.
Recommended for singles or couples (or close knit groups :-)