Well the simplest answer: because a roomba is not a living thing.
Regardless of how sophisticated Roomba Mk #9999 is in aping the behaviour of living things, it itself is not living and so is not sentient: "Sentience is the ability to feel, perceive or be conscious, or to have subjective experiences."
I'm partial to Roger Penrose' position on AI, and his interpretation of Gödel's incompleteness theorem and its implications for Strong AI.
It is impossible, and therefore futile, to create consciousness through construction of algorithms, no matter how complex, as the mind is non-algorithmic.
I know there was recent HN exasperation on the apparent 'misapplication' of Gödel's theorem to the mind / matter problem, but I"d dispute the implication that it is misapplied through ignorance. It is simply educated disagreement between two opposing philosophical positions.
Many of the issues around materialism / physicalism / computationalism and the mind / matter problem are covered here http://rational-buddhism.blogspot.com. Yes, it's from a Buddhist perspective, but you'll quickly find a lot of articles seem to cover the issues from a computer science perspective.
Penrose's position boils down to him being uncomfortable with the idea that Gödel's theorems might apply to himself. His books have received criticism from the majority of the academic community and his suggestion for where the non-algorithmic nature of the mind may come from has not seen empirical confirmation. Simply put, it is just wishful thinking.
Regardless, Penrose himself dismisses the role of any supernatural factors; this leaves us open to the possibility that a non-algorithic but nevertheless synthetic intelligence could be created (and in theory wedged into my roomba). Orch-OR does not require 'meat'.
