rosin to me is more of a dry agent, this is a tacking cloth, makes your fingers a little stickyI've never heard of it, isn't rosin just as good?
take this as a lesson,my dd was a 12u player last year and was pitching in a game,with light rain.She has GG and went to the PU and asked first.He looked at it and said she could use it.It just to me made more sense to ask first,then rather have problems later.If he would of said no even if it is in the rules,we would of said that it was fine.next time ask first,The umps arent there not to punish the teams and players,sometimes just asking can save a lot of pain later.