What is the common term for a small room typically used as a bedroom in Roman houses?

The term "cubiculum" refers specifically to a small room in Roman houses that served primarily as a bedroom. These rooms were essential to the layout of Roman domestic architecture and were typically located off the atrium, the central hall of the house. Cubicula were designed for privacy and often contained a bed and storage for personal belongings.

In contrast, the other terms represent different features or types of rooms in Roman architecture. "Alveus" is often associated with the central area of a Roman banquet couch or a type of seating rather than a bedroom. "Atrium" is the main room of a Roman house, notable for its open roof and central space, serving as a gathering area. An "exedra" refers to a space designed for relaxation and conversation, often featuring seating and sometimes used for gatherings, but not a bedroom. Thus, the specific function and design of a cubiculum make it the correct answer for a small room used as a bedroom in Roman houses.