Stuff it.
If you roll it, the fibres in the stuffing will be bent and stretched the same way each time. That way, it will soon start to be "uneven", as in, fibres gather in lumps instead of being evenly distributed within the stuffing. Each time you roll it back in the same postition, the fibres curl into these lumps, while it gets thinner other places. That is bad for insulation.
When you stuff, you even out these lumps before they start to form. You should not store a sleeping bag when compressed, though. Same as with rolling, you don't allow it to "puff up" again after compressing it. Ideally, it should only be in is cover when you are moving it, and be hung up - rolled out and stored in a large paper bag to absorb moisture - when it's not in use.
I tend to stuff it, and roll it out as soon as I get home. Let it dry and "rest" for a few days, then stuff it loosely back in the cover for storage.