NoseyChickens, I don't know how your coop is designed as for it's ability to be closed up at night, but if there is a way that you could close the coop up while the crow/raven was inside (trip cord on the pop door or whatever) and trap the crow/raven inside for a while that might do the trick. Then bang on the side of the coop a little and talk loudly and finally open the door waving a large towel around till he skeedaddles out of there. Basically you'd be instilling in him a great fear of the place. We accidently did more or less the same thing when we had a rather severe owl roosting problem in a warehouse....it worked, the owl never returned.
Of course crows and ravens are pretty smart critters and even after the scare I'm not sure it would say....... "Nevermore."
FWIW,
Ed