Rooftop Storm
Enchantment
You may pay 
rather than pay the mana cost for Zombie creature spells you cast.
"What nature creates cannot be unnatural!" —"Doctor" Zilky Grebbs
Dave Kendall
Innistrad Remastered (INR)
• #306Rulings
You must still pay any mandatory additional costs, such as exiling a creature card from your graveyard for Makeshift Mauler.
(wotc • 2011-09-22)
The mana cost and mana value of the spell are unchanged. Rooftop Storm only changes what you pay.
(wotc • 2011-09-22)
Rulings
You must still pay any mandatory additional costs, such as exiling a creature card from your graveyard for Makeshift Mauler.
(wotc • 2011-09-22)
The mana cost and mana value of the spell are unchanged. Rooftop Storm only changes what you pay.
(wotc • 2011-09-22)