Dual Wield

[Alram]

I've built a rogue who wielded 2 daggers and really enjoyed the fast attack speed. On my new Rogue I'd like to use a sword in the main hand for the increased damage and a dagger in the off hand to boost the attack speed.
1. Can I wield 2 unlike weapons?
2. How are the attack speeds determined? Does each weapon keep its stated attack speed? Or are they averaged? Or is some other formula applied?

Thanks.