Rocrail has a problem generating every time the right SHA1 key which is needed to accept the websocket.
Most browsers will write something like this in the Web-Console:
This is also the reason why the connection is not established between Rocrail and Rocweb.Error during WebSocket handshake: Sec-WebSocket-Accept mismatch
As soon as I solved this issue it should be better to make a connection.
So its not the browser, but Rocrail who has the buggy implementation. (Sorry FF.)