Do some searching before you make a new topic, all the answers you seek are out there, but I'll make it simple for you.
You can dual wield staves, yes. But as for shields; Nope. There was a rumour floating around for awhile, but it was concluded to be fake, and you cannot dual wield shields. Also, crossbows are not in the game. Source of the staff dual wielding: http://elderscrolls.wikia.com/wiki/Dual_Wielding, usually the info that ends up here is legit.
And by the way, a Skyrim related topic goes in the skyrim section.