Romist

a. 1716, Robert South, a sermon on Titus 1. 1. the Romists hold fast the distinction of mortal and venial sins

Source: wiktionary

The most tranquil period in the history of the country [Ireland] is that which marked the introduction of the Reformation. Had the antipathy been a religious one, it would have become, at such a period, intensely aggravated. It was remarkably otherwise. The most eminent of the Irish chiefs readily took the oath, and acknowledged the supremacy of the King; and, in the reign of Elizabeth, the whole country, priests and people, conformed to the reformed ritual. "The whole body of the Romist priests abandoned their connexion with Rome, and adopted the Protestant liturgy, and the entire mass of the population outwardly conformed to the ritual of the Established Church."

Source: wiktionary