I foam roll religiously. I don't know how I lived without one for so long.
While the jets feel good, and probably help to loosen up a bit, there's no way that you'll get the pressure you would from a roller. One of the best things for me is that it can crack my upper back, which is almost impossible without a good amount of direct pressure/weight.
One of the things that I sub in when I don't have a roller is a ball - a lacrosse ball, a tennis ball, whatever - roll it against a wall into all of your knots in your back and your hips.