Using rollers and small hard balls can be beneficial to helping you break up tight muscles and increase blood flow throughout your body. This doesn't replace regular flexibility work but used in conjunction can make a world of difference on post exercise activities and your ability to sustain your fitness levels longer.
There are a variety of rollers on the market that have a # of shape and sizes. The most important thing should be:


Comfort ( not to soft or too hard )
Portability
Price ( range $14.99 - $45.00 )
Use the roller as often as possible. A few times a day or a few times a week. But definitely make an effort to use this therapeutic tool. It can help relieve:
sore muscles
ache muscles
low back strain
upper back strain
tight hams
tight quads
tight calves
You can purchase 1 on Amazon or when your at the gym use the ones they have there.
Hope this information helps you.
Next Level Fitness
A.Pigott DC