You do not have to pay Magic Jammers cost. Magic Jammer's timing would be incorrect and it would be destroyed. You can however pay Magic Jammers cost to chain it to Bait Doll.
RoD has proper timing if there is a monster that can be targeted on the field and Jinzo is not face-up, so you must use RoD (you have no choice).DefiantUnycorn said:so if he Bait Dolls a face down Ring of Destruction...you can just say no i don't wanna blow up one of my monsters?