Roomba's will always have the possibility to run over and smear things around, while most things alive never shoop on the go unless you're a creature from the ocean or a rodent.
I choose the singular mound over anything a roomba sucks at it's job. Dogs can learn discipline (something i am very good at training animals), and roomba's sometimes don't know how to get home. The trick is to get the dog to eat it's own pile every time, and even to lick the plate/carpet clean. The problems and solutions of maintaining what is otherwise an organic alarm system. I will keep the alarm system. I tend to treat mine well so as not to eat feces. These alarm systems are capable of anything, and i do mean anything (have i mentioned eating poo already?).
You can even buy these alarm systems with different judgement and pedigree. The smaller the unit, it stays active until you kick its ass. While bigger more expensive units (because they eat more) have enhanced intelligence for determining what's a threat and not to determine next function (better than current artificial intelligence, the realization that friend/foe status is not static).
In alarm systems, i trust sheep dog and malemute brands as they will not help intruders out to plunder the house (i know it's a strange selection) and give both a rating of "very good boy".
Take that roomba!