Pass a class as a parameter?

It looks like you've almost got it. You want to pass [RootViewController class] instead of RootViewController. That gives you a Class value. Also, I don't think you want your function to take a Class *, just a Class. It's not actually an Objective-C object.

- (id)navControllerFromView:(Class)viewControllerClass

It's just Class, without the asterisk. (Class isn't a class name; you're not passing a pointer to an instance of the Class class, you're passing the class itself.)

rootNavController = [ self navControllerFromView:RootViewController

You can't pass a bare class name around like this—you have to send it a message. If you actually want to pass the class somewhere, you need to send it the class message. Thus:

rootNavController = [self navControllerFromView:[RootViewController class]
                                          title:@"Contact"
                                      imageName:@"my_info.png"
];