Hello Samfre, how much experience have you had with roasting? How much floor space will you have in the shop? Is the roasting for store consumption only, or will you be supplying wholesale clients outside? Post a little more and I think you will get some input from the guys here.
I guess you will have check zoning info with the relevant suburban authorities in HK. You may need an afterburner, but its a maybe only. There are numerous options open to you re roaster selection. Probably I would look at a small shop roaster, maybe a 12kg roaster +/-. If you have never roasted before it means you will certainly need some initial training on on the roaster you select. You could look at Diedrich or Ambex out of the USA. I know Diedrich has helped out some of the new breed of roaster setting up shop in Singapore. I would perhaps ask what your experience is in coffee to start with, your motivation to setting up a roastery. If you do not have any specialty coffee experience I would suggest you read Andrew Hertzels (cafemakers, who posts here) excellent article> http://www.cafemakers.com/coffee-business/intro.html .Certainly with investment in plant, packaging, espresso machinery...etc it makes sense to go down this path first.
I just got registered, so this is my first shot at this forum. I saw your question and thought I'd give you my thoughts. I've been roasting (not commercially - for me and my coffee-loving friends) for about a year using a hot-air popcorn popper. It sound like I might be just about where you are in thinking about opening a shop with a roaster.
I read a neat article in Roaster Magazine where a lady opened a shop using the Sonofresco fluidized bed roaster. (www.sonofresco.com.) It only roasts one lb at a time and costs less than $4,000. She has progressed to having five roasters in her shop now.
One advantage the Sonofresco has is the small investment. Spending $15 - $25K on a roaster that roasts 20-30 lbs at a time may not be what you want to start with, unless you know you'll have a large volume to roast. Of course, you could get a used one off Ebay for cheaper. The other advantage, at least in my point of view, is you can add additional machines at little cost, or you can upgrade to that big Diedrich if you want to.