I have a airbrush and am going to make roses in red and i have kroma kolor that i got from kopykake is the another way to get my roses really deep red
that sounds nice!!
I think if you make your roses with red icing and let them set, they should get really red. If it's not red enough or if you want to add some highlights/shadows, you can go over it with the airbrush too.
Earlene Moore sells a red coloring paste that she uses to get really deep red roses.
http://www.earlenescakes.com/store/colors.html it's at the bottom of the page and it costs $10 (US)
After you have made the roses red you can darken them with a
light spray of black or dark brown. You can test this on white paper first....