Anything said on a talk show has to be taken with a grain of salt. It can be expected that Rossie O'donnell will try to say things which will cause her show to be in the headlines. On the other hand I must admit that there are many open questions regarding the 9/11 incident. The biggest question that bothers me is the way the towers collapsed (Rossie's point as well). First of all it's quite strange that a fire managed to take down the whole building when taking in to account the steel support such a building has. Add on to that, the fact, that the building collapsed in a way that makes no sense when looking at the damage it sustained, and you'll come to the conclusions that something is off here.
I don't know if it's a full fledged conspiracy, but it definitely needs to be investigated.