I have just sent a PM to the creator of this beautiful cake, but I would like to know what kind of support system is used to make this type of cake? I would imagine that it takes a ton of roses? Do they just get stuck in there, or are they stuck into something?

Here is the link...
  http://www.cakecentral.com/cake-photo_94405.html

I have made this style and I use a 2 plate system in between with floral oasis stuffed inside. That way the flowers can site for a long time and you don't have to worry about them falling out either. Its also nice because you can transport each layer of cake and roses separately and its very quick to set up once you get there.

Wow, your cakes are beautiful!
I was told that you could also use the center column stand and that it is more sturdy. But you think that it would be OK and strong enough with just the plates and pillars? Do you use the hidden pillars?

I don't think you can get the exact same look because the plates on the tall tier stand will always show (they are slanted so you can't even use just a smaller one). I use drinking straws for supports inside the cake with the two plate system supporting between the cakes.