Every so often, we see things like "what if Rome had imported paper-making tech from China" or "suppose Rome had gotten the heavy plough from China"-- things like that. It's very true that for all of antiquity (and I'd say right up to the early modern age) the East was the developed world, and more advanced than the West. But besides the potential for the importation of interesting technology, this also led to a major problem regarding trade: Rome (and other polities of the West) bought stuff from the East, but had little to nothing that they could offer the East in return. The result was the gold flowed always East, and never West.
Basically, Rome had a trade balance problem. Gold flowed to Persia, to India, to China... and never came back. Whatever we may say about a trade balance issue in the modern age of fiduciary currency, in the days that gold was money, it presented a real danger. There are many theories as to the "decline and fall" of the Roman Empire. I personally think that the outflow of gold was a major cause. The gold supply dwindled, currency got debased, prices inflated as a result, an inflationary cycle got started, etc. Eventually, this led to dire straits, economically speaking. Taxes got raised to such a level that many common people could not bear the burden (the problem being that taxes had to be payed to the government in actual gold, while the Emperors issued increasingly debased coin).
It's even been suggested that this burden got so high that many common families could not afford to feed (enough) children, leading birth rates to dwindle to around replacement rate. This in turn led to a situation where almost all children would either have to take their parents' jobs full-time (such as working the farm), meaning they could not serve in the military. There were simply not enough 'spare sons' who could be, well... spared... to go off and serve in the military. Hence, increased reliance on foreign tribes serving as foederati. We all knew how that ended.
I'm not entirely convinced that this line of reasoning tells the whole story, but it's compelling even if incomplete. It would mean that preventing the massive outflow of gold to the east would prevent a lot of later problems, or at least work to make them less acute. The interesting thing is that while the economic understanding of the Romans was somewhat limited (they didn't really seem to understand the implications of currency debasement), there were certainy Romans who agitated against the outflow of gold.
So my question is this: what if Rome had forbidden trade with the East, with the specific aim of preventing that outflow of gold? Could such an injunction have been implemented? Roman-era economic protectionism: it sure would be interesting. I'm absolutely certain that it would have its own drawbacks in the long term (economic protectionism always does), but given the circumstances, such a policy may well be the smart move for the West until it has something valuable it can offer the East, so as to restore traade balance.
So far from trying to help the Romans by giving them nifty tech from the East, a good way to help save Rome may instead be... to severely limit Roman trade with the East. Could this have been done? And if so, would it have stood a chance of preventing Rome's worst problems?