I have two questions that I think I know the answers to, but it never hurts to ask...
#1: How do I secure a real fabric ribbon around a fondant covered cake?
#2: How do I secure fresh flowers to a fondant covered cake? (I want the flowers to cascade down the cake)
I use a bit of piping gel as glue for ribbon.
To attach fresh flowers to a cake I make clusters of flowers - like corsages. I use floral tape to form the corsages. I attach a toothpick to the corsage and use it to pin the corsage to the cake. I often make small flowers on the ends of toothpicks (gum paste or royal icing flowers) and use these to help pin the corsage in place, too. I make the sugar flowers to fit in with the arrangement. There is an example of fresh flowers attached this way in my photos. I used 8 flower clusters on Megan and Kyle's cake. The toothpicks had tiny pink royal icing rosebuds on them.
for ribbon i use a bit of double side craft tape, I think it is called monoadhesive, and use the permanant tape.
I second the toothpick.
My two cents worth: somewhere I read that you can wet the ribbon and then attach it to the cake. The moisture will help it adhere to the fondant. Haven't tried this yet, but is sounds logical.
I think I'll try the wet ribbon thing on my next cake. My last fondant with ribbon cake I used dots of RI every couple of inches and by the time I delivered the cake there were little "wet" dots all over the ribbon.