Store-bought fondant is expensive and making your own fondant is a fair amount of work, especially if you've gone to the trouble of dyeing the fondant in multiple colours. Yet, this is just the preparatory work. After you have prepared the fondant, there is the process of rolling it out, laying it on and pulling, pinching and smoothing it to create the perfect, professional-looking finish. If you further bring sculpted fondant into the cake decoration from delicate gumpaste flowers to sculpted ribbons and bows, it is a terrible waste to turn your cake masterpiece into a mess by improper storage.
Ideally, you should be able to place the finished cake in a pastry box and leave it at room temperature until the time comes to serve it. Fondant itself, a dough-like mixture made primarily from powdered sugar, needs no refrigeration. Indeed, refrigeration tends to soften fondant, leading to a sagging and gooey coat. Rolled fondant seals the inside of a cake, keeping it fresh, but fillings that always require refrigeration will still need refrigeration. It is best to use a cake filling that doesn't require refrigeration with a rolled fondant coating.
It you have used a cake filling that requires refrigeration, then cover the cake in plastic wrap before placing it in the refrigerator. When you remove the cake, keep the plastic wrap on the cake until it comes to room temperature to reduce condensation issues. Low moisture refrigerators are great when you have to refrigerate a fondant-covered cake, although problems with moisture can still arise.
If you have made the cake far ahead of time, you will need to freeze it. First, place the uncovered cake in the freezer for about 20 minutes to harden the fondant somewhat. Remove the cake from the freezer. Cover the entirety in plastic wrap, and then cover it in aluminium foil. Place the foil-covered cake in the freezer. To thaw, take the cake out of the freezer and either place it in the refrigerator for a few hours or in a space at cool room temperature. If you've placed the cake in the refrigerator, remove it after those few hours and let the temperature continue to rise in a space at cool room temperature. Do not remove the coverings while this process takes place. Wait until the cake has reached room temperature. This will take several hours.
Instead of preparing the entire cake in advance if you are planning on using a filling that needs to be refrigerated, just prepare the cake itself and coat it with buttercream. Freeze or refrigerate that and wait until the day of the event to place the fondant on the cake.
No matter how careful you are with refrigerating or freezing your cake, it will not come out of the process completely flawless, but the damage will be minimised.