Hopefully you haven't attached that "roll pin." There aren't any roll pins. What appears to be a roll pin is actually the locator tab for the Main Spring.
I haven't had a CZ apart in a long long time, but seem to remember, once you remove the screw in the side plate, you can work the side plate off beginning at the rear. there is a lip at the front of the side plate that holds the plates in the side of the frame. The hammer, is a functioning part of the the side lock action, and should remain attached to it's pivot thru the side plate.
These guns are a little rough on the inside but serviceable. I'd only council attacking the Main springs if you have already acquired an "OOPS" set of replacement main springs. There is also a "domino" effect. When you reduce the Main Springs, you should also reduce the hammer return springs and the firing pin return springs.
You may also wish to polish the barrel pivot and the locking lugs to give you easy opening.
Coffinmaker