Crinkle Cutter

no recipe tonight, just showing off a nifty gadget. my mother has a knack for finding weird little gifts and this year i had this in my stocking. i'm calling it the crinkle cutter, because i'm creative like that.
i attacked a sweet potato yesterday and here are the results:

roasted 15-20 minutes at 375 degrees with salt and pepper.
and yes that is my cookie sheet. it's disgusting, how do people keep theirs looking like new? am i doing something wrong? am i a bad person?