Final answer:
Revelation 22:18-19 delivers a threat to anyone who hears the prophecy and might add or take away from its words, which primarily targets readers and copyists of the text.
Step-by-step explanation:
Revelation 22:18-19 issues a stern warning specifically to readers who might add to or take away from the words of the prophecy in the Book of Revelation, which would arguably include not only the immediate readers but also those who would copy or transmit the text.
While the verses directly address "anyone who hears the words of the prophecy of this scroll" and therefore is inclusive of all those who come into contact with the text, the immediate implication would seem to focus on potential copyists who are in a position to alter the text. It's less direct in addressing gentiles, Romans, or any other specific groups unless they are in the position of being a reader or copyist of the text.