If I do a 45-day lock-in agreement for a customer and they close on monday, the lock-in expires on tuesday (during the 3-day right of recission), can the bank legally change the rate if the loan has not funded?

Your rate-lock agreement must have an expiration date. I'm no attorney, but I don't think the rescission period would have anything to do with the rate lock. As long as the loan closes before expiration of the rate lock, I think you have to honor it.

I would agree. Also remember your customer has signed the legal documents laying out the terms of the loan which includes the rate. The ROR is for the benefit of the borrower, not the lender. As long as the loan closes on or before the lock's expiration date I would say you are bound to that rate.

If the loan is a refi, couldn't the borrower decide to recind if you raise the rate? You would then have to return everything they paid including the rate lock fee.