3:21 PM PT -- A spokesperson for Rondell Sheridan tells TMZ ... "Thanks to all of the friends and fans who have responded so generously to Rodnell’s situation. He is extremely humbled by the love an support everyone has shown him during this difficult time. Diagnosed in early April with severe…

"That's So Raven" star Rondell Sheridan breathed a HUGE sigh of relief when he found out Christopher Dorner was dead ... 'cause they look so much alike, Rondell says he was legitimately scared to go out in public. Rondell -- who played Raven Symone's dad on the Disney sitcom -- tells TMZ ... ever…