When a roof leaks, the first question is whether it needs a repair or a replacement. The honest answer depends on three things: where the damage is, how old the roof system is, and what condition the layers underneath are in.
A repair makes sense when the problem is local. One cracked tile, a split pipe boot, or a bad piece of flashing at a chimney can all be fixed without touching the rest of the roof. If the rest of the roof is sound, spending money on a replacement would be a waste.
A re-roof makes sense when the problems are everywhere. If leaks keep showing up in new places, if the underlayment is brittle across the roof, or if shingles are curling and losing granules on every slope, patching one spot just moves the leak to the next weak point.
On tile roofs there's a middle option: lift the tiles, replace the underlayment and flashing, and reinstall the same tiles. You get a watertight roof again without paying for new tile.
Whatever a roofer recommends, ask to see photos of the problem and ask why a repair won't work. A good contractor can explain the recommendation in plain language. If we think a repair will do the job, we'll tell you, and we'll put it in writing.