Coming at this from decades of experience: from pan to popcorn popper (with many odd stops in between) and finally Hottop. So...
I guess this comes down to asking why do you want to take on this challenge? Then you've got to start considering just where you're going to put the little beast (how much smoke can you, and possibly your neighbours, and smoke detector live with?). How much money and time are you willing to devote? Assuming you're still game then it's onto how large or really how small a batch size do you want? Are you picky about roasting technology (drum versus fluid bed)? Are your target roasts for a basic brew or are you after espresso? Yadda, etc., whatever....
So what I'm "asking" the prospective purchaser is something more akin to a session with Freud (OK, so I'm joking, but just a little).
One should not take on this adventure lightly. And though we're not looking into climbing Everest or going to the moon it's still not the process of investigating the purchase of a toaster!
I suppose it would be nice to build a little program that leads to the right answer, but this is a road with many paths and much learning. Mistakes made lead to learning, and that's why I personally chose the path to coffee nirvana via home roasting (pardon the zenshit).



