Cubiculum: living room, for socializing reasons. They had

Cubiculum: the bedroom of a Roman villa
The Romans often thought the bedroom as a less important room compared to the rest of the house, even if all the grooming and dressing activities took place there. Thus it became a small room, quite crapped, thanks to the low vaulted ceilings. The average Roman bedroom was about 6 feet wide. The bedroom itself inside was not filled with much furnitures. A bed or a sleeping sofa to sleep on, a chest to put one's belongs, and a little footstool near the bed. The flooring would often be covered in mosaics, in a certain pattern that would eventually led or frame where the bed sits. Some bedrooms, like the ones discovered in Pompeii, would have a bed niche.
The windows themselves were even smaller; they usually were three by two feet. And if the bedrooms were on thefirst floor, the windows would not look at onto the streets, located near the atrium. Yet the room would nevertheless be situated towards the westward side, so that the windows would catch the morning sunrays. If the rays were bothersome, they did have shutters to block out the light and create a more dimmed, night-like environment. Sometimes, there would be a small antechamber in front of the bedroom chamber, where a personal servant would rest there, the antechamber was known as the "procoeton".
The Roman bedroom was often known to be small and more public compared to the Greek bedrooms. They were often located off the atrium, the entrance hallway, or connecting to the living room, for socializing reasons. They had bedrooms for the members of the family as well as for their fellow guests. The bedrooms during the daytime were used as a place to hold daytime private meetings, a place to have friends over, or to hold a confident business trading.
– http://www.tcnj.edu/~anchouse/bedroom.html
– http://www.roman-empire.net/society/soc-house.html