High performance engines like that Rossie can be hard to set up, yes. Usually because they are more sensitive to needle settings than sport engines. And that Rossie will probably have some very aggressive port timing which makes things worse. But if you are careful with your needle valve adjustments, they aren't really "harder", just more sensitive and "peaky". They also tend to be more sensitive to the fuel system set up than sport engines, so you need to make sure you set up the tank and such correctly.

I agree with what others are saying, start with a more mild-mannered sport engine, and better yet, start with a beginners kit or ARF that has the engineering done for you. Save your design efforts for later.

First, read the instructions that come with the engine. If the engine doesn't have instructions, get one that does.

Your best bet is to find some modelers local to you to get help directly. There are almost certainly people with experience near you.