I've got an Ozturk 10kg roaster that I have gotten good use out of. One big difference from other roasters is that the drum is cast iron, not steel. I've not roasted on steel but understand that the cast iron gives a "softer" more even heat. No hot spots. We get nice long (slow) mellow roasts from it. Seeing all the controls on some of the other roasters that the Ozturk doesn't have (or maybe they do now) I like to compare it to a Chevrolet or Ford. It's got everything you need and it gets you from point A to point B in comfort, just no heated seats, rear view camera, or 37 speaker sound system.
For heat control there is a screw setting on the valve controlling propane flow that you can adjust to increase/decrease gas flow. When we're roasting a small batch we adjust the heat down but we're just 'eyeballing' it. I would like a nicer way to adjust the pressure where I could also get a pressure readout, then it would be much easier to know when I'm roasting 3kg I need to set the machine to X or when I'm roasting 5kg it should be set to XX. I've looked here locally to try and find some plumbing to enhance our heat control but in Ireland it is tough to find things that are around the corner in the U.S. and then they only want to sell it to a certified propane person (they won't even sell you a length of hose here!)
That said I do think you can work with Yavuz Ozturkbay, to gentleman running the show, to fit the machine out with any extra bells and whilstles you may want on the machine.
There is a guy in New York who is an importer and he could give you A-Z the pros and cons versus other machines. Look up Adirondak Coffee Roasters on the web.
As to the reference about them being like an Ambex I heard, but have nothing to corroborate it, that Ozturk made the roaster frames for Ambex and then Ambex finished them up the way they wanted them to be.