Nothing comes to mind in Radium, but just down the highway in Invermere there is a place called Peppy's. They do pizza and some other stuff and I have been there twice and loved it both times. Very good pizza and unique concept.
Helena Stube's is a small restaurant right in Radium and has excellent food. It's not particularly fancy inside, but every dish is excellent. It's often full on a weekend evening so reservations are recommended.