I don't think that the price of foreign calls will be affected – everything is simply charged at the home plan rate. Calling e.g. a French number will cost the same regardless of whether I am in France or the UK.
To take three UK for example:
Calling Spain from the UK: 46p/min
Calling Spain from France while roaming: inclusive in minutes allowance, otherwise 3p/min.
It's a bit of a joke really. I don't know why the EU didn't think of this.
It's not within their power to regulate these charges.
Technically it isn't roaming and the telcos happily charge you premium as it does not fall under that regulation. Many people will be confused by this bit.