They come in two types: solid foam, with various surface treads and ones with a plastic inner core and an outer foam surface.
They are easy to carry and use and provide a perfect post-match/training cool down.
I highly recommend you try one a few times, you should notice the difference in a few days.
No for my confession: I don’t like them. I find them awkward to use, although I do see and feel the benefit.
I have an alternative which I will tell you about another time, but just because I don’t like them doesn’t mean you won’t.
Essentially, you roll your body over and around them and your body weight provides the pressure for the massage.
They can work the legs, back, shoulders and arms.
I’m pretty sure you local gym already uses them, so try and check them out.