Well first I would quarintine a new bird for 3-4 weeks then let them get to know each other thru a fence or cage for awhile then maybe let them range together for a week or so then put them together.
The pecking order is always going to come into play but they will work it out,and it will change as your flock ages it's just part of being a chicken. As long as nobody is getting really hurt leave them alone and let them work it out. You might might want to add an extra food and water source at least for a while to make sure you don't have a bully stopping the new kids from eating.
Every flock is different and will act accordingly just watch yours and they will tell you when to integrate. Just don't worry about a young roo he will grow into the job in his own time ,some are just faster than othersand even a mature roo will have to fit into the pecking order.
Dan