While Nintendo's official screenshots show some inklings using rollers on a Tower Control map, don't do it. I'm serious. There is virtually no reason to use a roller on a Tower Control map unless you are never going to stand on the tower itself.
The only practical use of the roller is to splash people with a wave of ink in order to free the tower for other players. However, the roller itself uses way too much ink for this to be effective, and using the roller means your team will have one less person to stand on the point. If you really want to take up the role of splashing players, use the bucket instead.