The problem with claiming the opposite, are things like Patton’s pretty much spot on prediction of the attack, the fact that intelligence at the time was routed through Washington, with capability to break the Japanese codes, or the still not declassified documents relating some pre-attack intercepts.
It all suggests that Roosevelt, and/or his staff, had all the pieces to figure out what was going to happen. Whether they didn’t, or did and decided to do nothing, and the lack of proof either way… is what makes the conspiracy theory keep being a possible conspiracy theory. 🤷