roofing with round blue gum poles

Hi, how's it going,  just want to introduce myself and pick your brains. I am a newbie here and want to say I've been fascinated by some of the posts here and looking for advice.
I am currently getting ready  to build a 2 bed room single story home in the middle of the bush in Kenya. A nice cosy home for myself and my wife ( a kenyan).
It will be L14 M  (45.9318 ft) x W7M (22.96ft) the structure will built using soil stabilized interlocking bricks ( lego). You can see the concept in the video.  Using these locally produced bricks cuts the building cost by approx 40% as it  is a much more environmentally sustainable option. It kills me that I have to use cement and all.
The roof will be a flat sloping roof  to harvest rain water as the area is semi arid.  My question here is, I want to use Eucylaptus  round poles as the rafters to span the roof. I really dont want to see any trusses for the aesthetics, I love a feeling of space  so can anyone tell me can I span the 22.96 feet with out using any addititonal support using 6-8 inch poles.
If it comes down to it  and I have to support I would like to use to a pole spanning the length in the centre with the rafters resting on this and  supported by  2 vertical poles that become a feature  ( 12 inch diameter)
The roof covering will be either makuti ( grass) or a steel sheets called mabati in Kenya. So weight is not a major issue and if it ever snows here then I am in big trouble.  
For the building permits we have to use an architect, after 3 attempts I am still having issues with architects not fully grasping the concept I have for the house, they keep coming back with sawn wood trussed structures for the roof.  I do hope someone here can advise on the roof structure as architects and engineers I have talked to here just  are stuck with the easy solution.

I am toying with putting a rammed earth floor in, when done here and sealed,  the colours of all the different elements in the red soil is amazing.  
We will harvest our grey water through a mulch tank then  to 2 x 55 gallon tanks with a gravel filter in the first, activated charcoal in the second ( home made using lemon juice to activate it) then it shall go to a natural pond for filtration by reeds, rushes and other plants and this will be used to water the  garden. We will use a composting toilet so no water waste there and no need for a septic tank.  
I do hope someone here can advise on the roof structure as architects and engineers I have talked to here just stuck with.

The  top 3 foot of soil is called black cotton, great for growing things, not so good for building on, so we have to excavate all this out for the foundations, then backfill.  But as the site is large we have just planted a fruit orchard and some indigenous endangered trees, later as the trees grow we wil keep a couple of hives for Honey and grow all our own veg.