An editorial answer separating a way of arranging garments from the container used to organize them.
1 answer
You can do both. Rolling is a way to arrange a garment; a packing cube is a container. Roll suitable clothing inside a cube, fold other pieces inside the same cube, or use neither if a small loose load is easier to manage.
Choose the garment method first. A soft T-shirt can form a manageable roll, while a collared shirt may be better laid flat with fewer sharp bends. The aim is to fit the item without creating pressure points or making it difficult to retrieve. There is no need to force every fabric into one method.
Then ask whether grouping the clothes solves a problem. A cube can keep underwear together or let you move the next day’s clothing out as a unit. It may add little when the bag contains only a couple of garments and you can already see everything.
Try the same complete clothing load two ways and compare access as well as space. A tiny volume saving is less useful if finding socks requires unrolling the wardrobe. Keep the arrangement that makes packing, using and repacking the bag straightforward.