My P.O. released me unexpectedly, so there was no preparation time to find housing. 1/2 way houses will take months to get into. Does the probation and parole office in Janesville, WI 53545 have to give me a voucher to stay somewhere?

No, you are responsible to find your own place to live.

There should be shelters, he may provide a list of shelters for you.

I do not know the law in your jurisdiction, however I would guess that no, they are not required to provide housing to you. Though, typically the department is helpful in helping you find housing as it is in the best interest of keeping you out of prison to have you housed.