There may possibly be a connection as outlined above by Lie-in-KIng, but I have to say that the scholars at The Oxford English Dictionary - the 'bible' of English etymology - say that the origin of rozzer is unknown.
I'm certain they would have been familiar with the ideas in Cassell, but they obviously did not find the link convincing. Accordingly, neither do I, but you are, of course, perfectly free to take your pick, R1G.