Only bmobile Everything Plans have in-package roaming bundles. The bmobile website can provide details of in-package roaming bundles. (https://bmobile.co.tt/mobile-4-2-2/#posteverything ).
If a customer has purchased a Postpaid Roaming Add-On, this will be depleted first and then the in-package bundle will be depleted, assuming that the in-package bundle is applicable to the roaming destination.