I left my rollers on and never had a problem. ... Nylon melts at 428 degrees and at that temp, its not smoking it's more like grilling or baking ... I smoke at no more than 220 so all the worries puzzle me. Bacon I cold smoke, under 100 degrees.
Regarding paint I built hot fires in each of my drawers and the paint only discolored.
Buy a lead test kit at home depot for $10 and test for lead buy squeezing the tube and rubbing on the paint.
I did pull the roller assemblies out of my cabinet, started charcoal in all the drawers, put the drawers back in the cabinet without the roller carriages, inside temp got to 550. left it at 550 for about 10 mins and removed the drawers to prevent warpage.
After all of it cooled down the I put the roller tracks with the nylon rollers back in except for the bottom drawer where the burner is.
I use the nylon rollers in mine when I smoke and haven't had a problem.