Covering a DIMM slot isn't an issue, the height of the RAM fins is what you need to worry about. Pretty much every decent cooler now will hang over the memory area so you can't get RAM with tall spreaders.
The Ripjaws series don't have fins, only a little bit that sticks up, so you'd be fine with pretty much every cooler out there - it's not tall enough to get in the way of the cooler or the fans.
So, as asked above, what's your case and how far do you want to push your overclock? These factors will influence your cooler choice, but your RAM isn't going to be a problem.
Kingston HyperX or Corsair Vengeance is a different story altogether (Google some pictures to compare them to the Ripjaws and you'll see what I mean).