If my roofer employs a private company to file for a supplement, do I keep the money or does the roofer get it?

The customer who is involved in a claim with a roofing contractor is kept to the side of the issue in general. That means that a customer, you, is not really a part of the roofer's liability insurance policy and does not receive any money regarding that claim. The money is, however, supposed to be used to make whatever repairs or pay whatever bills are necessary to cover the damage done by said contractor. There isn't much else to say on it. If you need legal advice I personally would recommend speaking with a lawyer. It's possible this could be a tricky situation though. For example, if I was your roofing contractor, and I have a liability policy, supplemental or not, I use any money I get from that to cover damages done by me or my crew when they are covered by it. That's the purpose of the insurance and ultimately the money goes to me (the contractor) for my business and fixing my issues. The construction contract probably has something about this in the details as well. Something about damage being the responsibility of the contractor to make repairs during or immediately following a construction project. I would double-check your contract and possibly hire a lawyer if it becomes that deep for some reason.

Here is a link to a letter about this topic, maybe it will help you.
http://coloradoroofing.org/member-folder/PDFs/PublicAdjusterAdvisory2018.pdf