Rem,
The biggest problem with Iowa public land...is there isn't very much of it! Iowa ranks 49th (out of 50 states...!!) in the percentage of land which is public- 1.04%- roughly 370,000 acres- much of that is NW Refuge and Corp of Engineers land along both the Mississippi and Missouri rivers. The amount of public land that is "prime" pheasant country is pretty small, and quite spread out.
With that caution, let me assure you that you can, and will find some roosters on the public land! I hunt public, generally starting the third week of the season, and rarely try it on the weekends! The NW 1/3 of the state has been the best for the last couple of years. Get a good guide, like the Iowa Sportsman's Atlas, start driving, and take a look at every public spot- some are small, but can be overlooked, and just might hold a rooster or two!
Expectations...?? If I down a bird a day, on public land, I am satisfied...at my age, the hunt is more meaningful than the harvest...but I do like to see the dogs get a retrieve, and I get a nice meal for later!
No generalities on how the birds behave- other than roosters, after the first few gunshots of the season, become extremely paranoid- they do what they have to do to stay alive. Most will try to run, some will sit tight and hope you and the pup walk by; I think a quiet, thoughtful approach to the field, and a relatively quiet trip through the cover will give you a good opportunity to score!
Good luck!