make your character(model in workspace) archivable, cut it, stop, paste it into workspace, and use model resize plugin.
if siggy == false then print"nooo :(" end
test
select your character
copy
paste
export as obj
open in blender
open paint.net for mtl file
edit mtl file (b/w)
insert mtl file to your mesh
then use sculpt mode
make it look jagged
import to roblox
done