This is a very interesting question which occupied me for a long time. I agree with L. Russo that a "scientific revolution" really happened in Hellenistic Greece. It actually happened
2 centuries before the time of Hero, at the time of the first Ptolemy's. Hero himself was probably not a great inventor, he is famous mostly because his book survived. Unlike the books of great scientists of the previous epoch. The fact is that scientific revolution started and finished in the period of less than 200 years. At the time of Hero science in Alexandria was already in a deep decline (if you compare with the period 200 years before).
There is no clear explanation why this happened, but this story shows that for an industrial revolution, scientific revolution is not sufficient. One needs some social conditions for an industrial revolution, and these were not present at that time.
Scientific inventions (of the time BEFORE Hero, when the true scientific revolution happened) were actually used in technology, especially in the military technology. Advanced military engines, enormous ships were built in the Hellenistic era.
(See "Helepolis", "Leonrophoros", "Greek and Roman artillery" in Wikipedia, as some notable examples). But only scattered hints of this remain in the surviving literature.
It is true that decline of science and technology coincided with the time of the Roman conquest. But I am not sure that the Roman conquest was the real reason of this.
(If the Hellenistic society were an industrialized society, how would the Romans conquer it?) Another thing is that the Romans borrowed and adopted almost all Hellenistic culture,
why did not they adopt also the science and technology?
The Romans annexed Egypt shortly before the time when Hero lived. Science was already in decline.
The school of Alexandria was not destroyed by the Romans, it existed for several centuries
after the Roman conquest, and in the second century AD it produced Ptolemy,
who lived in the times of Trajan, and in the 3-d century there was Diophantus.
Science in Alexandria completely disappeared only with the spread of Christianity. This shows that the Romans did not "eliminate" or prosecute Science, they tolerated it. They just did not care about it.
This is really strange. There were many well-educated Romans, some of them even wrote on science (Pliny, Strabo, Plutarchus), but they were not interested in doing it! You cannot find any true mathematicians or astronomers in the whole history of Rome, though there were certainly some engineers. (Of course, Ptolemy lived in the Roman empire, and probably was a Roman citizen, but nobody counts him as a "Roman").
The short period of explosive development of technology ended a generation before Hero.
(And there was apparently a short revival about 100 years later, I mean Ptolemy).
And on my opinion, the reason why science did not lead to a real industrial revolution lies somewhere in the social organization of society. Whether this was slavery or not, I am not sure. But it looks like "capitalism" is a necessary prerequisite for a true
industrial revolution:-)
EDIT. On my opinion, another good example, that great scientific discoveries do not necessary lead to industrial revolutions, is the history of science in China. The ancient Chinese invented paper, and according to some sources, even the printing press. This on my opinion is a much greater invention than a steam engine. Printing was invented in Europe in 15 century,
and look at the consequences! And compare them to the consequences of these inventions in China. Same in the military area: the Chinese invented gunpowder and rockets, and probably guns. And what happened to all this artillery when the Europeans arrived to the Far east? Chinese had to adopt European technology. There are many examples like this. The military of Byzantine empire was probably very advanced. They had advanced ships and they had this mysterious "Greek fire". But they were defeated by a less technologically advanced civilization, and all their inventions were forgotten. I think something similar happened to the Hellenistic civilization.
