Where Roman coins have been found

One of the dots shouldn't there, just saying

Source : https://en.wikipedia.org/wiki/Asterix

Doesn't show the Han/Byzantine trade: https://en.wikipedia.org/wiki/Sino-Roman_relations

Roman coins have been found as far east as Vietnam and Japan.

It looks like coins have been found on the sea routes that avoided the Parthian/Sassanian empires, but not on the overland routes. I’m guessing merchants exchanged their coins on the Roman/Persian frontier, east of which the Iranian coinage was the standard anyway; but in politically fractured places like southern India (south of the Kushans and Guptas), Roman coinage became the de facto currency of international trade.
So in other words, the distribution of coins outside the empire reflects a regional demand for mutually-accepted coinage, rather than Roman trade per se.

I’d have guessed more would have been found in southern Italy.

Can't find them in a place that you don't look.
Rather, that part of Italy might not be interested in looking (or might not be publicizing when they do).
- Sure they would.
The reason for that is that people in the heart of the empire didn't feel the need to hoard coins and bury them since they weren't nearly as exposed to barbarian threats (and others) like the areas on the fringes of the empire.
- Dude the vast, vast majority of found coins found weren't buried intentionally.
  By some estimates there were BILLIONS of Roman coins minted. They're absolutely all over the place.

Wow, they did not fuck with Ireland

Nothing worth pinching
- The potatoes are amazing. Cause real trouble when they run out. /s
  Edit: /s added for clarity.

Wish I could see a map like this with the finds colored by mint date.

Anybody got some juicy (scientific) context for SW India and Sri Lanka? Commerce I suppose but in details, what, how and when? And how are you BTW?

A fascinating primary source is the Periplus of the Erythraean Sea(link to a complete translation in the article).
There's a book covering it:
https://en.wikipedia.org/wiki/The_Golden_Road:_How_Ancient_India_Transformed_the_World
Also, fine thank you.
Spices.
I guess pepper is largely in the "what" mix

I live kind of in the middle of several finds in an area without any. I wonder if that means there aren't any, or no one has bothered to seriously search for them.

Grab your shovel
- Already have a detector and permit. But I still need permission from the farmers/landowners and that's trickier.
Maybe it's up to you to start digging

i like how they skipped over saudi arabia but got to yemen some how

Possible that there aren't as many archeologic diggings there
Aden in Yemen has been a major port for the trade route to India since at least the time of the ancient Greeks.

Amazing, thanks a lot.

Very cool map I haven't seen before, thank you!

It's so strange to me that the Romans went through central Europe, were they just taking the land route to the sea nations up north?

Yes—the Amber Road, the main trade route to the Baltic, did go through Central Europe.
And the reason trade went overland instead of by sea is because the Romans weren’t trading directly with the Baltic—they were paying soldiers stationed along the Danube and Rhine who then traded with neighboring peoples (and also directly subsidizing some frontier tribes), and the frontier peoples of Central Europe were then trading Roman gold for Baltic amber.

Southern Italy has always been poor. Water, infrastructure and so on

How Italy Became the Most Divided Country in Europe

The source of the map is not provided in the OOP.
I think it’s very likely this map is biased in reporting.
I’ve heard roman coins are really common in some southern regions of italy. Perhaps to the point where finding them isn’t reported, and doesn’t end up on this map.

Well after Rome fell the currency was worthless, what else would you do with them? I mean it took 1500 years for them to be worth more than the metal they were minted on.

Not worthless. The coinage had intrinsic value, being made of metals with a commodity value. So it's not like holding a paper banknote when a government collapses. People would still have used them to hoard savings, for trade and melted down as a source of precious metals.
That was really the only value they ever had. Boosted a bit by confidence in the purity (but also reduced when Rome debased its coinage).