[inquisitor]

Originally Posted by wco81

Has any carrier expressed any interest in building a Pan-European network?

It depends on what you understand by a Pan-European network. Given that licenses and spectrum are still assigned by the national regulators, you can integrate core networks but for the radio access network there are limitations resulting from the national circumstances. That said I know that Vodafone has integrated and unified a lot of infrastructure including their roaming hub which I think is located in the Netherlands and handles roaming traffic for all the European Vodafone networks.
The EU Commission - once again - is unrealistic in this regard. There's no unified legal framework and no consistent regulation for Pan-European networks but they demand such to be created by the private sector anyway.
I definitely applaud such efforts, but I believe it's done wrong like most things that come from our Brussels bureaucrats.

The EU commission said roaming fees revenues are only like 5% of total revenues?

Probably on average, but I'm sure that there are EU countries with a significant higher share of revenues that come from roaming, especially those who have much tourism. Once again the discrepancies among member states are neglected by centralistic Brussels.

What is more likely, carriers trying to build networks in all regions or trying to come up with roaming agreements.

That's impossible because on the one hand there is no spectrum available in most countries and on the other hand there are numerous smaller players in the EU who lack funds to expand into other EU countries, which by the way do all have highly penetrated markets so it doesn't make sense to compete with the incumbants.
By this new regulation the EU will squeeze those smaller undercutting players out of the market, harm competition and foster oligopols. As a result consumers will have to pay higher prices in their home countries just for saving a few Euros during their holidays.

I understand that one of the issues with having global LTE devices is that the carriers haven't sorted out the roaming fees for 4G. I guess I shouldn't be surprised that they might want a premium on 4G roaming fees but OTOH, 4G prices in the US at least aren't higher than 3G data contract prices.

LTE roaming hasn't been implemented on a larger scale because it's still complex and expensive for operators while there's no consumer demand for it as long as data roaming is that expensive. Who would even pay a premium for having their data allowance eaten up in even shorter time?
Also the fact that LTE networks still cannot handle voice calls (VoLTE has still not been deployed) but require a so-called circuit-switched fallback (CSFB) to GSM or UMTS makes it quite complicated to provide LTE roaming service with the required reliability.
European operators indeed try to sell LTE at a premium, which will fail as hardly anyone needs double digit MBit/s in their pockets while UMTS still provides decent datarates in most of Europe. In the US things are different because price levels are higher than in Europe and American operators face a capacity bottleneck on the air interface due to high smartphone adoption rates and limited 3G frequency spectrum. So in the US LTE is more about taking off load from 2G and 3G networks while in Europe it's more about creating a premium service which they hope to sell at higher prices.