It's still ambiguous as to whether they actually vacuum. The Roombas that my friends have just sweep the floor (although that is still fairly effective). The subject line of their press release suggests they do utilise vacuum cleaning now, but the description further down still skirts around the issue, calling their tasks 'cleaning' rather than 'vacuuming'.
Regarding robotic butlers - I'm sure the Roomba could be utilised. Give it a cute little bow tie, park its recharging station next to the drinks cabinet, and deposit dust next to your sofa.