They seem to available at https://gitlab.freedesktop.org/wlroots/wlroots/-/releases/0.15.1 e.g. https://gitlab.freedesktop.org/wlroots/wlroots/-/releases/0.15.1/downloads/wlroots-0.15.1.tar.gz.
that's already the case (see 0.15.1-r1) SRC_URI="https://gitlab.freedesktop.org/${PN}/${PN}/-/archive/${PV}/${P}.tar.gz"
or are you wanting the release and not archive? if so, why?