It would be dangerous to transport you back to Roman times, because you might teach them to write C++ and compile it into cellular automata, and then program Empire with a 30 million soldier human computer, like the "human abacus" scene in "Three Body Problem"!
Of course you're right!
After much thinking about it, providing a printing press would be the most effective invention to bootstrap a modern society. And, well, that's exactly what happened after Gutenberg invented it. The greatest inventions in history are:
1. writing
2. phonetic alphabet
3. paper
4. printing
5. networks
And the pattern is obvious!