I think there are several things that are known:
1) FDR wanted into the war because he believed that a Nazi Germany in control of the bulk of Eurasia was a potential threat to the USA.
2) He knew he couldn't get a declaration of war through Congress.
3) He had tried provoking the Germans in the N. Atlantic, but they wouldn't bite.
4) The US in negotiations with the Japanese presented them with humiliating terms, which there was no chance of them accepting.
4) When the Japanese rejected the terms and the US embargo was imposed, FDR knew very well that it would lead to war.
6) The US military was expecting war with Japan (there was a 'general war warning' sent on 27th November, so the attack was very far from being a 'bolt from the blue'.)
5) The US knew that Japan was going to attack US interests on the 7th Dec because the declaration of an end to diplomatic relations was intercepted and decoded the day before before it was presented by the Japanese ambassador.
6) Some intelligence officers recognised that the timing of the Japanese declaration coincided with dawn in Hawaii but failed to persuade more senior officers to pass on warnings until it was too late.
The above isn't necessarily a 'conspiracy' though.
The evidence that FDR knew of the attack on Peal Harbor and deliberately sacrificed it is thin at best, but the theory at least has a basis of fact in that the generally held 'bolt from the blue' legend isn't true.
This article reviews the evidence often brought up by revisionists.