My roof is leaking. What should I do right now?

First, deal with the water inside. Put a bucket under the drip, move furniture and electronics out from under it, and if the ceiling is bulging with water, put a small hole in the lowest point of the bulge with a screwdriver to let it drain into the bucket rather than letting it bring the drywall down. That sounds drastic and it is the right call.

Second, photograph everything: the stain, the drip, the bulge, the damage to anything below, and if it is safe to do so from the ground, the roof above it. If this turns into an insurance claim, those photographs are what the adjuster will want.

Third, do not go on the roof. A wet roof is dangerous at the best of times and the leak will still be there when it is dry. If the roof is actually open, a tree through it or a section stripped, that is an emergency tarping job for somebody with the gear.

Then get it looked at while the stain is fresh, because the entry point is far easier to find when the water is still moving. Tell the contractor when it started, what the weather was doing, and whether it leaks in every rain or only in wind-driven rain, because that narrows it down considerably.