If I change the jstl dependency to provided scope in the pom, ROO will re-add the dependency the next time I run the controller scaffold command. The end result is I now have jstl defined twice in the pom. Once without scope and once with provided.
This should not happen with any dependency, so I am not sure if this is specific to the addon-web-mvc-controller or it would happen with other add ons as well.
This is related to