Any cards are that are cast go onto the stack according to the turn order
Rooftop storm is likely one of those cards wed ask people to cut in upgraded precons, as people optimise the manabase, ramp, zombies, payoffs, draw and interaction, a card enabling you to do a bunch of things for free on top of that is likely not healthy to keep for BC once a deck is upgraded
The first thing to consider is the way you want to build a deck
It can take the strenuous detail out of something so you can just have good fun with it
Next Tuesday, look forward to my card preview article for the upcoming Universes Beyond release, Magic: The Gathering Assassin's Creed
In this case, the free spell lets you (or another player) create a copy of one of your creatures