RAM that is somewhat tall, like G.Skill Ripjaws X, will just barely be too tall, unless you're only using only two RAM slots and use the dual channels furthest away. Alternatively, you could move the fan "up a notch" - but you will lose some efficiency.
I have an ETS-T40, which allows for one more millimeter of clearance, and it barely allow a piece of paper to pass through - too close for comfort.
If you have the before mentioned Corsair Vengeance LP, or G.Skill Ares style of RAM (or just RAM without heat spreaders) you'll be fine.