I know of a person who has done this swap and it was a breeze. Have fun though with the bottom race!

It's the same with the OEM's.
You are going to gain some friction when compared to the ball bearings. Also you can over tighten the triple clamp nut with less risk of buggering something up before you stop tightening things. With the roller setup you'll have more surface area making contact. If your shock loading the stem (Doing Wheelies) these bearings are for you! I'll stick with the balls as hey seem to do the job well enough for me. I replaced mine at 11,000 miles and found no wear when I installed a new adjustable triple clamp.