Every broiler is different, so watch them closely. If your garlic is getting black or dark fast, but is still hard inside, move the pan to a lower level or turn them over. You want them soft on the inside and will be taking off the paper coating. If your tomatillos start to blacken, that is your signal to also move them down a rack, flip them over and keep roasting until just softened and juicy. Your blender should puree a little dark spot or two, but you don't want them all blackened.