I've never punched anyone with a roll of coins. Just thinking about it, I think it would increase the force of the punch without adding any (or enough?) protection to the hand.
I can say from experience that sawn off shovel handles and concrete blocks work well in protecting your hands. I know a guy that prefers to grab opponents by the nape of the neck while landing a body blow(s) with the other hand. Then using the hold at the nape of the neck to propel his opponent's face into walls, trees, cars or whatever massive object is available in the vicinity. I've watched him do it. Works very well for him. He likes guys with ponytails
For myself, I will not be delivering full power blows with my fists to an opponent's face or head in a real fight as opposed to a formal match.