Does the wizards simulacrum melt when the scroll is used? Or can the wizard make gold off scribing scrolls. I’m asking because the wizard is heir to a ruby mine but doesn’t want to be like his father so became a wizard. Long story short is he has the rubies taken care of, and I don’t want to go into the endless army territory. Thank you.
The spell on a scroll is cast by its user, not its crafter
Presumably, you are worried that using a spell scroll would count as a spell being cast by the person who crafted it, thus triggering the destruction of a simulacrum. However, when a spell scroll is used, the caster is the one using the scroll (emphasis added):
If the spell is on your class’s spell list, you can read the scroll and cast its spell without providing any material components.
The "you" in the item description refers to the user of the scroll. Hence, when a scroll is used, the one who crafted the scroll is not casting the spell, unless they also happen to be the one using it.
Nothing happens to the wizard’s simulacrum.
If you cast this spell again, any duplicate you created with this spell is instantly destroyed.
The wizard would have to cast the spell again to destroy his simulacrum. When someone else uses a spell scroll the wizard made, that someone is casting the spell, not the wizard, so someone else casting the spell doesn’t affect the wizard’s simulacrum.