This is usually caused by mixed getWriter() and getOutputStream() usage on an HttpServletResponse, i.e. by mixed textual and binary content generation on the same response. I've also seen this caused by a JSP trying to forward to a binary download controller - with a bit of comments/empty lines having been generated by the JSP before, and the response having been flushed already.
Anyway, jay, it would be good to see your stacktrace here. Could you post it?
I have tried to replicate the issue with the latest STS release without success and I cannot see anything in the stacktrace that indicates an issue within the core framework. If you are still having issues I suggest raising a bug with the Spring Roo team who will be in a better position to track down the root cause. We can reopen this bug if it turns out not to be something specific to Roo.