Advice on rendering schmaltz
Most of the fat has already been rendered out of roasted chicken skin. I wouldn't bother trying to render more. Crisp it in the oven, crumble it roughly, and sprinkle it over things, if you're looking for something to do with it.

As for rendering schmalz, it's not difficult. Go slow and start with a bit of other fat if you're not using a non-stick pan.