If you had a Roomba, especially in the early days of the robot vacuum, it was in many ways a fairly unsophisticated machine. It would just bump around your house, looking for something to suck up, until its battery died or its (way too small) tank filled up. Not that it mattered, though.
Source: [The Verge](https://www.theverge.com/podcast/953275/roomba-robot-vacuum-version-history)