I did this same thing on my performer. Just cosmetic for me as they still work fine.
After a comp I put my 18"WSM grates (2), my 22" WSM grates (3), and my uncle's 2 grates off a barrel smoker, all covered in grease and bits of fat/meat on my perfomer over a bunch of coals. Turned around and there was a 2 ft flame coming out of the top, so I threw the lid on. Left the vents open for a minute, and I guess it melted the rollers.