Is Romanism the Same as Cultus Deorum?

Yes.

Romanism is the contemporary practice of Cultus Deorum which is Latin for Cult of the Gods.

The name Romanism was popularized by protestants who observed how the practices of the Catholic Church were derived from Ancient Roman Religion. Since we follow from the Roman Catholic lineage, the name, Romanism, is more appropriate and understandable to modern people than the Latin term Cultus Deorum.