Replacing a single roller on an unloaded section - door down, spring tension released, panel off its hinges - is within reach for someone comfortable with a wrench and a Saturday. It's one of the more forgiving garage door repairs, because the roller itself carries no stored tension.
Where people get hurt is skipping the step where you confirm the spring tension is actually off before working near the bottom section, or working on the top roller near the track end cap without knowing it can pop loose under the door's own weight. If you're swapping one roller on a door with 2,218-households'-worth of neighbors who've mostly got the same late-90s hardware, parts are easy enough to find at a hardware store. If you're finding three or four worn rollers at once, that's usually a sign the whole set is near the end of its life, and replacing them one at a time as each fails costs more in truck trips than doing the set once.