I rarely roll for monsters, weather, NPS personalities or anything like that. I homebrew all of my settings, and I place encounters right where I think they will be most fun, using monsters that make the most sense to the environment.
BUT...
I L-O-V-E love to roll on random treasure tables. After two hours of planning out a dungeon and statting out monsters, rolling on the treasure tables is like getting dessert after you've cleaned your plate. I always save it for last.
Though there was this one time...
I sent the players through the Temple of Law-Fallen-to-Chaos (sounds cooler in draconic), and absolutely everything came off of a random table, including random effects from Jester's Insane Chaos list. My favorite dungeon, and a fan favorite.