Saruman's Ring

[Rumil]

My take on the rings of Saruman (not just one ring but ringS) is that they aided him and his underlings in sorcery (for want of a better term)

Perhaps they enhanced Saruman's power of influence and the power by which he confined Gandalf to the roof (difficult to explain by other means?) Could they have given him greater power over the orcs and Dunlendings? Did he give out rings to lesser or apprentice sorcerors in order to 'light the fire of Orthanc' at Helm's Deep or did they simply have to light the blue touch paper and retire 20 paces? Did his rings confer invisibility - unlikely as I believe Gandalf says that only the rings of power can do this (I may be wrong, can't find the reference)

Sorry for lack of facts, just speculation, but as has been said before, JRRT didn't really expand on this subject.