You should only refridgerate your fondant cakes as little as possible or not at all. I would say NEVER freeze them.
What happens is the fondant gets very gummy and loses its shape from the condensation. If you put your fondant cakes in the fridge over night, you will most likely wake up to your cake falling apart.To store at room tempurature:
Make sure you keep your fondant cake covered in Saran wrap or a covered cake plate as your fondant may dry out and crack.
One thing I like to do, so that the saran wrap doesn't acually touch the cake ruining the smooth surface or decorations, is:
I place the cake in a cake box and do a quick saran wrap cover over the box.
The covered cake will keep at room temperature for several days.BUTTERCREAM
Buttercream on the other hand can be frozen or refridgerated without consequence.You can also read more about fondant cakes in this post