What happened to the Roaming King game for the online multiplay? It was playable for some time and now it’s a game called Grifter
343 has limited-time social and competitive playlists that will get rotated in and out. There will always be an event calendar on Halo Waypoint that allows you to see what is coming and going. But to answer your question, Roaming King has been rotated out, and replaced by Grifball.