At risk of going off-topic, they did show how Saruman died at the start of ROTK, but it was edited out because they thought instead of telling the new story they were stuck on the old one. (A mistake Lucas made in ROTS and perhaps the whole PT).
The Extended Edition DVDs of LOTR do show the cut out scenes. Worth watching for 'closure' but IMHO the cinema versions are better: they edit stuff out of films to make them better. In the directors commentary of EE LOTR they tell you 'We cut this scene out because of XXX' Jackson and his two writer/producers also admit (and argue) over the claims they made the movie too long. Compare that to Lucas' silly defensiveness over his SW writing: just plain silly.