Most Romans (excluding the salves who were not Romans despite being the majority in Rome) would have been better off with a good steam engine. However before you get to good you need to go through a lot of working toys that are not worth having. Tractors (tractors have replaced almost half historical human labor, with various automated spinning/weaving machines most of the rest - everything else done by humans, slaves or not is a footnote) are vastly better than slaves, but there is a reason when John Deere bought a tractor company in 1918 they wrote all their dealers something to the effect of the horse drawn plow will always be the backbone of the American farm - early tractors were not better than human labor in general.