When you chair stays in one place for any length of time it creates grooves where the wheels are. So it's just as hard to get out of those groves as it is rolling your chair along the carpet that the mat is on top of.
I purchased this to go on top of the carpet in my office and it does work but it is thin. I would go for the next one up if I were to purchase one again.
Not wanting to damage the carpet pile under my rolling office chair I checked out Staples and found the 36" x 48" clear mat which is a perfect fit and my chair rolls easily on it.