We have been doing roof repair out of Garfield for 25+ years. Paterson is 2.8 miles north-west of the shop, in Passaic County — close enough that we are on these streets most weeks. Either way we still answer when you call about the job two winters later, which is the part that actually depends on being local.
A repair starts with finding where the water is actually getting in, which is rarely above the stain — water runs along a rafter before it drops. Then the failed component is replaced rather than sealed over: flashing, a valley, a pipe boot, or a section of shingle.
Passaic is really two counties. The southern cities are dense and old — turn-of-the-century multi-families and row homes packed close together. North of the reservoirs it turns rural, with lake houses and wooded lots that were often built as summer cottages and later winterised. Older roofs are usually an accumulation of several eras, with additions and junctions added over a long life. Working out which one is leaking takes longer than on a single-build roof, and it is the step that decides whether the repair holds.
You get photographs of what we found before we price it. Sealant is a maintenance product, not a repair, so if a joint has failed it gets replaced. And if we get up there and conclude the roof needs replacing rather than repairing, we will tell you that instead.