You want a toe? I'll get you a fuckin' toe.
-- Grima Wormtongue
When does Saruman 'weild fire'? That's more of a Gandalf thing what with him having Narya, the elven ring of fire. Cirdan even specifically gave it to Gandalf when he and Saruman were both arriving at the Grey Havens. Saruman never does fire stuff.
In one of the deleted scenes from the film, Saruman throws a fireball at Gandalf. He's already weak and defeated, so it's really just a show of spite, and Gandalf destroys his staff as punishment.
You could also make the argument that Saruman's "cunning" use of fire is in the furnaces under Isengard, or the bomb he made for the attack on Helm's Deep.
The deleted scene fireball is a movie invention. The helms deep bomb is described a bit vsguely described as 'blasting fire' and there is some evidence that he got this from gandalf via the hobbits. Merry and Pippin find a bunch of barrels of pipe weed from the shire in Orthanc, which establishes Saruman has some dealings in the Shire which is then used at the end of Return of the King in The Scouring of the Shire and Gandalf was always bring fireworks around and it says he was famous in the Shire for having the most wonderful fireworks, not the only fireworks. That leaves furnaces, which is a bit weak.
Yup. And considering hobbits were making their own fireworks, it's more than plausible that Saruman got his hands on them through the same channels, explosives tend to draw interest in a world without them, so he may very well have gotten his hands on some the same way. He may also just have already known how to make gunpowder like gandalf did. He was a servant of Aule before being sent to middle earth. I like the hobbit explanation though cause it fits really well thematically and characteristically. Saruman was a good manipulator and good at using other people's tools to his own ends but tended to shit the bed at creating his own stuff.
