Gelatin for gravy?

I'm coming from a r/keto perspective and missing some of the awesome times I've had with gravy over my roast. they don't like flour over there, or corn starch, or wondra, or anything else with carbs. Well, they (we) do, but we want to save them for good, veggie-related uses.

Can you offer advice on the use of (knox) gelatin as a thickener for gravies?