How to properly use vases and rose bowls (glass) to support and/or separte a cake?

I haven't done it myself, but you would still need to use supports in the cake that you are putting the bowl or vases on. So you would support it the same way you would if you were putting a cake on it instead of a bowl.

http://www.wilton.com/cakes/tiered-cakes/fluted-bowl-set.cfm

Thanks for your help.

You are welcome.