Since the mother provides the type and I have a lavender roo it seems it would be best to get black hens instead of getting a black roo. But the thing is the black roo would be easier to keep compared to lots of black hens on top of lavender hens. So that is why I am asking how many black hens would you recommend there need to be? I hope this makes sense.
Some believe this to be true... in my experience the roo lends just as much to type as the hens do.
My advice would be to use your Lav roo over Black hens, hatch lots of chicks and grow them out, keep the F1 roo with the
best type and as many of the F1 pullets you can manage. From there breed these birds together. You can cull your original Lavender roo, as you no longer need him. You have the Lav gene in your F1 offspring so that is all you need from their sire.
Breeding F1 X F1 will produce a number of visibly Lavender chicks. Again, hatch as many chicks as you can possibly manage from the F1 X F1 breeding, grow them out and keep those with the best type. Also of the visibly Lavender chicks keep those with the best feather quality.
At this point I would select a F2 Lavender roo with the best type and best feather quality, if you have more than one great keep as many as you can manage, and breed him back to the
original Black hens that you used,
assuming that they still have superior type to your other F1 or F2 birds. At this point you're starting the described process above all over again.
Over time with each generation you should see improvement in both type and feather quality. Producing quality Lavender birds will take time, patience and a heavy hand when culling but if you're committed the project the resulting birds have the potential to be very beautiful.