Slaves might explain lack of interest in labour saving technology in general, but the steam engine in particular mostly excels at stuff which slaves couldn't do (high speed transport) or enabled production processes particularly well suited to slave labour (textile mills vs craft-textile production). The UK's Industrial Revolution began with slave-picked cotton being spun on machines attended by abundant unskilled labour and powered by watermills, a technology the Romans (and many other non-industrial civilisations) exploited with smaller scale machinery.
The Romans valued research and engineering highly enough to be way ahead of both contemporary and successor civilisations in many aspects of it and have people willing to document their pure research into steam (which as the article acknowledges, turned out to be at best orthogonal to the pure research that got us pistons and condensing engines), they just didn't have all the intermediate inventions like high quality iron, rail lines and spinning jennies to make large scale use of steam that the British did 1500 years later, the same level of demand and competition for new products etc etc. But the abundance of cheap labour was something they actually had in common with the British Empire; it's just the British Empire used it differently (and displaced even more cheap labour by killing off craft industries as a result)
> the steam engine in particular mostly excels at stuff which slaves couldn't do (high speed transport) or enabled production processes particularly well suited to slave labour (textile mills vs craft-textile production).
I think there’s a bit more to it: “high speed” is something which took a long time to be true. A lot of these things were simpler applications which seem to have big situational components: if you have literal tons of coal and ore to haul, plus relatively amenable terrain, but not competition from boats, iron to make rails and boilers, and a good source of fuel (coal or wood) steam engines are a great investment. Similarly, if you have fixed industrial demand and abundant fuel but not water power, stationary engines make sense.
If you have different answers for enough of those points, it’s hard to justify the development - it took the Europeans a couple of centuries in starting in the 1600s, after their population already exceeded Rome’s, and as you mentioned they already had or started a lot of related technologies, too. An agrarian society, a hilly one, land without lots of easily available fuel, etc. might not have had it ever make sense or only after someone else has made multiple generations of technology development.
The Romans valued research and engineering highly enough to be way ahead of both contemporary and successor civilisations in many aspects of it and have people willing to document their pure research into steam (which as the article acknowledges, turned out to be at best orthogonal to the pure research that got us pistons and condensing engines), they just didn't have all the intermediate inventions like high quality iron, rail lines and spinning jennies to make large scale use of steam that the British did 1500 years later, the same level of demand and competition for new products etc etc. But the abundance of cheap labour was something they actually had in common with the British Empire; it's just the British Empire used it differently (and displaced even more cheap labour by killing off craft industries as a result)