If a roller is sitting just outside the track and the door is still square, you can sometimes walk it back in by hand with the opener disconnected - pull the release cord, brace the door, and gently guide the roller into the channel while someone else checks it's seated. That's about where DIY should stop. A door on original 2002-era track is usually running under spring tension that a homeowner shouldn't touch, and if the track itself is bent or a bracket has pulled from the jamb, forcing the door back onto it just loads the next roller to fail the same way. If the door won't move freely by hand, or the track shows a visible kink, leave it alone and call it in rather than working the opener against a bent rail.