Launch Manycam and on the Effects tab, go to "Text over video" and uncheck the "Show Manycam.com logo" to remove the watermark.

On the ChatRoulette website, choose Manycam as your camera, press the "Preview" button and then press the "Allow" button in the popup and you should see whatever you have selected in Manycam on ChatRoulette.


I use freeware Splitcam for Windows instead. Can't try this on a Mac,...

By the way, not only Splitcam allows to use your web-camera with many applications, but also you can use a video or a picture instead of your web-cam. You can even use chatroulette if you don't have any webcams!