Fire crews responded to the blaze at 10600 Randy Lane around 2:20 p.m., fire officials said.
Arriving crews found light smoke coming from the rear of a single-story house with a detached garage.
The homeowner was in the street when crews arrived and said the garage roof was on fire.
Firefighters found a resident on a ladder using a garden hose to try to extinguish the small fire on the wooden roof of the garage.
Firefighters took over and quickly extinguished the fire, officials said.
Crews left the scene at 4:15 p.m. after PG&E crews arrived and inspected utilities.
The cause of the fire appears be to a cigarette that was thrown onto the garage roof by a resident in the home, officials said.