The lack of a remote makes the chromecast a non-starter for me. Let's say I want to pause a movie (a fairly common task). With the Roku, I press a physical button without having to look at the remote. Chromcast = Power on device, enter unlock pin, dismiss lingering notification from facebook, text, etc, open app, pause.
I've used idevices as remotes on and off for years. They are a miserable experience compared to a simple remote like the roku.