If plants were human, we might say they're schizophrenic. Part is always searching for light while another part is busily running away from it. And while leaves and light are useful for producing food, roots are equally essential, stabilizing, gathering nutrients and soaking up water. The more of them, and the longer they are, the better.
And roots are supposed to be invisible, safe in the soil from quick changes in temperature and moisture. The most vulnerable part, the single cell thick root hairs, crowd around the growing tips. You'll rarely, if ever, see them.
But whenever you expose a root these are your first concern. The root itself may seem plump and unchanged by ten minutes of exposure to air, but the root hairs will probably have shriveled and died. Regrowing them will take time.
So get the roots from pot to soil as quickly as possible. Or, if you're moving a plant from one place to another and can't dig them in right away, cover the roots with soil or plastic as they wait. And if you lose quite a few in the process, take off an equal number of leaves to reduce the evaporation and consequent moisture draw on the whole plant.
And, after having customers rave about SuperThrive when I worked at a local nursery, I always add some to the water that "settles in" a plant after transplanting. It has a long list of ingredients including vitamins as well as small amounts of the same rooting hormones used to root cuttings. Since you only need a few drops to be effective, the price tag for the bottle isn't as intimidating as it seems. I alway put some in a dropper bottle to make sure I don't use too much.