Is it acceptable that a 15A circuit be branched to multiple rooms?
It's perfectly fine to have a single breaker service multiple areas of a house, and in fact, the code doesn't say too much about that beyond certain places require dedicated circuits (eg: kitchen counter outlets). The code limitation only comes from circuit load and the size of the breaker and wiring.

Practically speaking, it's nice to limit the scope of a single circuit. 

For example, I try to do one of:


Single breaker controls all outlets/lights in one room only
Single breaker controls all outlets/lights in two or more rooms
All outlets in one room are controlled by two or more breakers, but those breakers don't control any other rooms.


I also generally try to keep lights and outlets on separate circuits, but that's not always practical. It is nice when a circuit breaker blows that the lights don't all turn off as well, and it makes working on things easier (you can either use the lights or plug in a light). 

I personally find it dumb when one breaker controls part of the outlets/lights in one room, and part in another room or area, but there's nothing technically wrong with it. I dislike it because it's not intuitive, it's harder to shut off a room, and the breaker labels are really hard to write and understand. At best your breakers get labelled stupid things like "N wall, green bdrm + S Wall blue bdrm + Hall + Bathroom lights".