I think he was aware, just didn't care and wanted to give Roy the impression of having outsmarted him.
Well I do admit its somewhat of a stretch, but the Oracle from Matrix (who was also just called "the oracle". Coincidence? :) ) did the same. "No Neo, you're not the One", even though she knew he was. He had to raise to that on his own, not because some Oracle told him.
Oh and I never said (if it sounded like it, then I didn't want to say it) that it is the Oracle's big master plan. The Oracle might just be a tool for Tiamat like Redcloak is for the Dark One.