Collisions for my circular platforms please...

I’m creating a platform game. I created the platforms in Blender. Then, I exported to Unity and all was correct. The platforms hasn’t got collision and my carachter falls. The platforms are circular and I can’t put a box or sphere collision. I only can put mesh collision but I have a lot of platforms and for this reason my game gets a lot of time to start.

Have you got some idea for make collision in my platforms?

Thanks and Happy New Year!!!

http://unity3d.com/support/documentation/ScriptReference/MeshCollider-sharedMesh.html

So pretty much it is just:

platformCollider.sharedMesh = platformMesh;

lots of thanks but… my game spend a lot of time to start with this script…and I haven’t got any mesh collision, all my objects have this script!

any idea to start the game more fastly?