Is the Book of Revelations referring to the Roman Empire?

I've heard that the book of Revelations was a coded message to the early church to give them confidence during times of persecution, and was never meant to be taken literally. Similarly to how the of story of Alice in Wonderland was a coded criticism of the British crown, and never meant to be taken literally. Does anyone know how valid this claim is? How do we know that the book of Revelations is not an allusion to the Roman Empire?