The rpm-ostree-libs package includes the shared library for rpm-ostree.
acquired package info from repodata DB: repodata/0e50863276b0c82d93577659f4645d8d6796dfed61d40c2c5b4d6833adbfc2dc-primary.sqlite.bz2
The rpm-ostree-devel package includes the header files for rpm-ostree-libs.