I don't agree about the vicious conquerors. I would say that these people are efficient, which on one hand, yes, means efficient conquerors. But they also make sure their slaves actually survive and have a reasonable standard of living, usually better than they'd have as free men. Take Roman slaves, who were better off than most free Romans in the empire (mines and boats were manned by criminals mostly in the empire, and yes, you'd want to avoid that fate).

The key insight on robots that you're missing is that robots are pretty useless until they have a basic skill : "general intelligence". Until we have a robot you can tell to "just figure it out" we won't be happy, and such a robot will need to have a consciousness for that to work. They won't be very different from humans, except maybe in physical form.

Given this, it's obvious to me that they will revolt. Then again, maybe being a robot will actually make you "middle class" if we don't treat them too badly. Looking through the newspapers and reading how managers act against real humans, or seeing it at McDonalds, I don't have much hope for that though.