I have seen several cakes with the wire in the cakes with fondant balls on them. Most on topsy turvey cakes what kind of wire do you use and do you stick in straight in the cake or do you insert a coffee stirrer in first for you insert the wire in??

Florist wire... use coffee stirrer, straw or floral/posey pick.
Choose the gauge of wire by what you want it to do. Stiff & straight = 18or 20g. Bouncy = 24g or 26g (These can be curved and twisted too.) Bend a little hook at the top of the wire before you place it into the fondant ball so that it hold securely.

What size wires do most use for making gumpaste roses?

I use 18g for the rose, 26 or 28 for the leaves.

Thank you so much...I have seen the wires in packages before but to pay 5 dollars for 5 of them will get pretty expensive...I will try this...