The foam roller is actually incredibly useful, I'm totally addicted to it anyway.
If you have one at home, you just have to find it, or I can safely recommend buying one.
I use it to strengthen the core and other muscles, not least I use it as a type of self-massage to relieve muscle tension/trigger points. And it actually works!
It works incredibly well (even if it hurts when you hold it), and there are countless good strength exercises you can do with this roller.
You can use the massage as part of the warm-up before strength training, as well as after the training as a good ending.
You can of course also use these exercises as a separate session, as I often do.
In the video below I show some of my favourites.