Armadillidium vulgare

The typical roly-poly, literally called the common pillbug. Like many other isopods they're native to the mediterranean but have spread out extensively, coming with us as we spread. The fact they're so common makes them one of the most studied isopods as well. Unlike A. nasatum, they're noticeably shiny, "taller", and don't have the little nose protrusion on their face. Often, they'll have little flecks of yellow going down the length of their body, which is usually grey in the wild. In the northern hemisphere, they breed once a year and mothers have been seen staying with their (usually about 100) babies after their release from the marsupium.

this page is a REALLY good source.

My experience

I find these outside a ton but haven't seriously kept any myself. I've found them living alongside other species, usually nasatum. Very common so not much to say here but I like their little faces.

Some morphs (there are way more)

When individuals of random morphs are sold in a group, it's called a gem mix.