I have a mixed flock of roos, hens and pullets. I feed starter/grower still with oyster shell on the side.
My roos and laying hens are 22 weeks old, the pullets, 12 weeks old.
My eggs are very hard shelled, the hens are eating the oyster shell when they need it. I will switch them all over to layer
feed when my 3 EE;s start to lay. I have heard Flockraiser is better when dealing with roos, with oyster shell on the side
for the layers.
I figure my roos will be ok with layer feed...I will mix it with whatever starter/grower I have left to transition them over.
Hope that helps, it's just my way of doing it, others do it differently.