In My Vodafone, by logging in here, under the "My Account/Call Analysis" section, specifically in the "Call Category - Roaming Calls (Roaming)".

In the My Vodafone app, by downloading the PDF with your bill analysis in the "My Account/Analysis" section.

On your bill, usage and charges during roaming are shown in the bill analysis under the field "Your detailed communication while you were abroad".
There, in the "Your calls…" field, outgoing/incoming calls are included; in the "Your text messages…" field, outgoing/incoming messages are included; and in the "Internet usage…" field, the MBs you used while using the internet abroad are included.