Bride wants fondant roses cascading down sides of two tier SMB covered cake. How do I get them to stay? Attach with toothpicks? Edible glue?

If you are still going to make the flowers, do them  on toothpicks and push in. If already made on wire,cut to the length you need and dip wire in melted choc. then insert or make small cascading bouquets, tape together and insert in straws at different level. Keep in mind not to make them too heavy at the edges, might tear the cake with weight and gravity. I use bubble straws to insert my flowers. HTH.