Drag Race Universe is GONE! Why?

Roku has no control over third party apps or if they decide to remove their channel.  It is possible that the license to broadcast that content has expired.  It appears that it has been pulled from other broadcast channels as well, such Free Vee and Tubi.  It may be a temporary thing, or the owners of that content have decided to cease broadcasting, or maybe they ran into some copyright ownership issues.  You could do a search and see if there are other channels that have it available.