At present, definitely not. Goodybags are not currently used to fund roaming of any description -- though having one qualifies for a reduced rate within EU.
The rules are changing and from mid June it's expected that people on all networks will be able to roam "like at home" within EU rather than having to pay differently for roaming data. But a fair use policy is allowed and its unlikely that your usage will be unrestricted.
In any case, UK goodybags haven't had unlimited data for two years. See https://community.giffgaff.com/t5/Tips-Guides/There-are-NO-UNLIMITED-DATA-GOODYBAGS-on-giffgaff/td-p/18905878