You only need one free hand to cast a spell, releasing a staff with one hand is a free action and regrasping it after casting the spell also a free action. DMs may limit how many free actions you get... However two is not too many.
Example: Juggling... how many catch and releases are there in 6 seconds.
This thread was started 4 years ago when the rules didn't allow releasing and re-grasping. The rules have changed since then. Let's allow this thread to go back into the grave from which you have raised it.
