As a long term foam roller user, I can tell you that a foam roller will improve your life. I’ve owned the solid foam ones, the Rumble Roller and the hollow Triggerpoint Grid roller.
But the Triggerpoint roller is the best overall and will last for ages. http://www.chainreactioncycles.com/ie/en/trigger-point-grid-foam-roller/rp-prod70385
The solid foam ones tend to go soft over time (like a cushion) and you’ll need to replace them sooner. They can be ok for the first while and they are a bit more gentle when you’re starting out. But as your muscles become less tacked down, and your roller gets softer, you’ll inevitably buy the Triggerpoint Grid roller anyway.
The rumble roller is nice to have as a second plan of attack to work out some particularly stubborn knots that you can’t get out with a smooth roller, but it’s not as versatile and I wouldn’t suggest it as an intro to foam rolling.
Have a look at mobility wod for some great ways to use them, as well as other life-changing mobility tricks http://www.mobilitywod.com
And there are more mobility (torture) devices on here: http://www.rogueeurope.eu/mobility-rehab.php (i’m a particular fan of the lacrosse balls and the voodoo floss — you have to try it to believe how good it is)