For big signings when the books were sent to JK to sign, it is said Roz signed some [most? All?] I've heard Mark Evanier has also done it.
The only SA sigs I have from JK are on a stack of Xerox copies of all the FF #14 page stats. Mike Royer purchased them in 1969 (he can't recall from who) from someone who already had JK sign one of the pages. Soon after JK first contacted Mike about working for him, Mike had him inscribe another of the pages. His sig was quite different then, but has recognisable characteristics.
Mike was going to sell them to someone a few years ago, but the guy never returned to finalize the transaction. Lucky for me