"draining fluid from your legs"

[Zen]

Muscle soreness and edema (the original query) are two entirely different matters.

Edema is an accumulation of extracellular fluid that Dianyla referred to. It's explained in detail here.

Soreness after exercise is due to an accumulation of lactic acid. That's when you get out the rolling pin.

[Starfish]

Zen, so if you are rolling toward the lymph ducts (like up the leg, and toward the groin area), doesn't that help kind of flush both lymph goo (to use a technical term) to where it needs to go, and lactic acid out of the muscles at the same time?

[Zen]

That's a good question.
I had one year of anatomy & physiology, I only know enough to get myself into trouble
It sounds good in theory but I'm thinking maybe you'd still have to elevate your legs above your heart because if the valves/gates aren't working right you have to give them a gravity assist to open.