As it is my first hunt I would rather spend more money on trophy fees that are the animals that are and will be most wanted.
I saw wild roan in Caprivi. And many roan and sable in the fence
Generally roan and sable are most valuable premium plains game. As a general rule, they will always be kept in a fence on a game management farm. Nobody is releasing them in the wild. They are valuable,
So, if you are happy with hunting in high fence, place to look is South Africa, and Namibia.
If you want wild roan and sable, no fences and free roaming: you look in Botswana, Mozambique, Zimbabwe.
But daily rates and hunt costs will be much higher.
I can recommend an outfitter in Namibia with 5000 hectares fence (12.300 Acres), if you drop me a PM.
Roan and sable are true fine trophies.
But experience of a hunt on a farm is different story.
For example, hunting a common duiker could be much more challenging and cheaper then hunting sable or roan in same place.
Bottom line is: I am not sure, is it worthy to chase top plains game trophies on a first safari, if this is your first safari?
I have hunted most of common plains game species in Namibia, plus I made one DG hunt in wilderness (Buffalo in Caprivi).
And I am still not ready to pay the trophy fee price for Sable and Roan in the fence.
I told my outfitter once if there is a sable and roan, old specimen, with broken horn or both broken horns, on very discounted price I will hunt them. No other way for me. With prices of roan and sable in the fence (which is one hunt, 7 days) I could get at least two PG safaris with more trophies of less expensive animals, and making hunts more challenging (and most likely I will go this route).
When comparing South Africa and Namibia, sable and roan fenced are generally cheaper in South Africa. But fences are in average larger in Namibia (not the rule, but in general)
Looking in this problem, and based on your inquiry, first question must be: how large is the property, and what is the trophy fee?
And consider broken horn discount, as well.
Before that you must be clear with yourself, what is the smallest size of fence you will accept. (this you did not clarify in first post)