Merging a new flock with a existing Rooster?

[Str8]

Hello everyone!
I am new to the chicken scene but jumped in head first. I started by purchasing some baby Orp Buffs from the local feed bin. I also picked up a existing flock of 2 year old RIR's. 9 Hens and 1 Roo. His name is Rusty. My Orp Buffs are 8 weeks old now and living is a separate coop connected to the larger coop. I am afraid I and going to have to meat out the 9 RIR Hens. One because of their age and another is because I do not think I am going to be able to merge the two flocks together. They are still producing about 4-6 eggs a day. Along with having 14 teenage Orp Buffs I also have 5 teenage Guineas that are in the coop with my Orps. They are getting along great I might add.
My main question tonight is does anyone think I will be able to keep Rusty (My RIR Roo) and merge him with my Orp Buffs as the Head of Household without any casualties?

 

[coffeychicks]

I was able to merge 3 flocks in one. What I did was when we free ranged we let them all out at once. 2 acres to sort it out but how their own coops. We have since joined all the coops and birds to 1 big happy family. Let the babies get to about the same size as others