If they are in good shape, and very specifically if the track fits the new rollers… If new rollers are too small or too large they will have issues traveling in the track.
Old rollers bearing blow out and fail over time, and generally over time there are minor changes in how big the rollers are, probably specifically to make the installation a bit more expensive with a new installation. The other issues with the old track are that it can get out of true (level, parallel, straight, etc… ) old track often should be at least re-adjusted, which can often take longer than installing new track (and will cost more due to labor hours) So it depends.
If you’re doing it yourself and have to squeeze the pennies… you CAN re-use track. It will take a bunch more effort to do it right (in researching correct rollers, measuring, bending, perhaps re-welding joints, cleaning, leveling… ) so yes, but it isn’t always the most time-efficient, and can, if done poorly, cost more than replacing the track due to failure on the door due to poor fit.
If the rollers are right for the track, and the previous door didn’t fail by coming out of the track (bending it on the way often) you can keep the old ones… installers would rather use the new track, as it eliminates all the potential issues, and allows you to have a warranty which if you re-use the track probably not.