Before I go and over engineer a problem, I thought I would get every ones expert advice first.  It clearly has worked well for me in the past. (Thanks Grayhawk) 
 
I have what feels to be a classic case of warped rotors, but that isn't it.  About the last half of the roll out I start to get a vibration from the right main gear.  Or at least I think it is the right side.  Thinking it was an easy fix I replaced the rotors with a new set.  I think it is better, but that could be just in my head.  The vibration is much worse under braking, but does exist while just rolling.  As most vibrations, it seems to have a peak intensity at a certain speed. 30-50 mph I would guess.  This has the original rubber cushion landing gear.
 
So, here are my ideas..
 
Bad tire that is out of balance?  Waaay out of balance. They are Chang Shin tires, so maybe I got what I paid for.  haha
 
Out of Alignment? This aircraft has had the service bulletin completed regarding the main gear reinforcement.  Could this have caused an alignment issue? 
 
Nature of the beast?  It has had this problem from the day I purchased it, so maybe it is just me. Although I hope not!
 
Would love to hear some ideas or past experience with this.
 
Thank a ton!
Tom McNerney
N54SG