Rokinon 10mm 2.8 Question

I just picked up the Rokinon 10mm 2.8. I was well aware that it's a manual lens, which is fine since it's only going to be used for Astrophotography. I was under the impression that I had to manually change the aperture. While testing it in the store I kept getting the fEE error. The guy in the store told me that I had to set it to f22 and then use the dial on my D7100 to change the aperture. I went home and did some testing to see if that was the case. I set it to f22, stopped it all the way down in camera to 2.8, removed the lens and it was still at 22. I did some research and found a possible solution, I have to go into the settings and change the aperture setting to Aperture Ring instead of command dial. It seems to work, I took a photo and the camera shows it at f2.8. My question is does setting the aperture on the lens to f22 and using the command dial really work or is it just the camera thinking that the lens is stopped down to whatever I set it to?

I borrowed one for about a month and started out with the EE message. Than I read the manual and set up the Non CPU lens and followed the manual on setting up the Aperture. I think the D7200 and D7100 are very similar. One I did that I want to say I used the front wheel to set aperture just as I did with a regular lens. I also used the dot in the viewfinder to help confirm focus when manually focusing the lens. It worked great.