Roofing in Las Vegas is a sun-bake first and a storm almost never. Composition shingles lose granules, curl, and dry out in the underlayment while the sky stays blue for months. The leak, when it comes, comes on a rare rain and looks sudden. It was not sudden. Tile cracks from heat and from being walked, and the underlayment beneath it can be finished while the tiles still look presentable from the street. Foam chalks, blisters, and opens at vents and curbs. West and south slopes die before the north slope on the same house. That is the local pattern.
Do not wait for a monsoon narrative. This valley does not give you one. Do not wait for snow. Look from the ground for bald patches, granules in the gutters if you even have gutters, cracked tile in the gravel, and foam that has gone chalky. Say whether the ceiling stain appeared on the only wet day you remember, or whether a bath fan or a vent has been dripping in dry weather. A dry-weather drip is often a boot or a flashing problem, not a field problem. A wet-day surprise on a tired field is the sun finally getting an invoice from the sky.
Ask for the scope in writing. Boots, wall flashing, underlayment, and what happens if the deck is soft. A granule touch-up is not a tear-off. Tile work has to protect the field from foot traffic. Foam work has to happen in conditions that let a coating bond, not at the meanest hour of a summer afternoon. Ask who hauls debris and who pulls the permit if one is required. Ask how a west slope is being treated differently from a shaded slope, if you have both.
The roof has been cooking whether or not you have had a storm this year. Say the material and what the ceiling did. Call the number on this page.