It all depends on the chemistry of the roosters, and hens.
Roosters raised together do better; however, I've not always had good results mixing in a single Silkie into a large fowl flock. Many birds tend to pick on the Silkie, especially the head notch, which can cause irreparable damage to the Silkie if they are hazed hard enough.
My banties do better if they are in their own separate area together.
But I've got friends who have banty roosters that rule the roost.
So back to it all depends on your flock.
9 hens to 2 roosters is a lower ratio...usually it is 8 to 10 hens per rooster, but that number changes according to the chemistry of the flock as well, and if the boys get along, and if they don't try to over mate the hens.
You can slowly work up to it and see how it goes. Have a plan B if it doesn't.
LofMc