Here is the URL of the cake she likes and wants me to do.  

http://www.wedding-flowers-and-reception-ideas.com/ribbon-wedding-cake.html 

Scroll down and it's the first picture.  

So the ribbon will be champagne and will either be actual ribbon or fondant.  I'm going to try both and see how it looks.  

The cake will be ivory buttercream. 

The roses will be between the tiers as shown.  THIS IS WHERE I NEED HELP.  Suggestions  on rose colors needed. 

Thanks! 

i would go with what the description says

"The delicate champagne colored ribbons around this fondant cake give it an elegant polish of sophistication. Bridal white roses are tucked all around into each tier."

and i would use wilton ivory color  and use more in the ribbon so it's darker and less in the icing so it's lighter -- it's futile to try & match those light off whites -- the lighting changes everything -- just use white roses -- so long as they all match you're good to go -- you want that to contrast like that --