Recent scholarship has suggested his role was massive. Both in setting up the conditions and badgering the Soviets for the nukes that set things off, as well as for increasing the possibility of nuclear war by encouraging belligerence and pre-emptive attack. The resolution of the Crisis was in part a routing of Castro's influence by both the US and the Soviets, neither of whom felt they could really deal with him or give him what he wanted.

The book to read is Sergo Mikoyan, The Soviet Cuban Missile Crisis: Castro, Mikoyan, Kennedy, Khrushchev, and the Missiles of November.