I concur with Martin. Practical tasting skills are critical. This is how you'll know what results are possible and which results you want for your business, how you'll learn to identify problems and likely causes of those problems, how to determine if you're achieving the results that you're aiming for, how you'll describe coffees to your customers and communicate your needs to your suppliers. There are some key tasks that you can do to develop those skills at different stages in your development:

Taste as many coffees as you can. Try what your potential competitors are doing, seek out roasters who are doing different things. Look for coffees from different countries using different post-harvest processing techniques. Taste light roasts, dark roasts, and everything in between. When you start learning to roast, taste everything you do, especially the mistakes. Origin trips can be a good way to try things that your suppliers are hopefully not exposing you to. More extreme examples of things like under-ripes or processing mishaps will help you identify more dilute examples that might slip through. Get in the practice of taking notes. Those notes don't need to be overly formal, though it's not bad to get in the practice of filling out cupping forms. On the high end, once you start sample roasting you can buy auction sample packs as a relatively affordable way to get lots of very high quality distinct coffees from the same whatever the auction is focusing on.

Learn cupping methodologies. Cupping is the lingua franca of the coffee supply chain and you'll have more success communicating if you speak the language than if you're doing your own weird thing. While all the details of sample preparation and scoring are geared toward sourcing, the mechanical aspects of cupping can be adapted for use in roast exploration, production quality control, and determining substitutability. There are classes out there that you can take at training labs or trade events as well as resources for sensory training. I'm not saying you need to become a Q grader (though CQI does have a good program), but getting good at cupping opens up a lot of opportunities.

Don't do all of your tasting alone. Different people have different sensitivities and different vocabularies. Talking about what you're tasting after everybody has had a chance to do their own initial evaluations can clue you in to nuances that were less obvious to you. There are good conversations to be had about how different samples might translate to production roast levels or red flags on coffees that could degrade badly before you get it. Try to get an opportunity to taste coffees with the sales person you're buying green coffee from and have those conversations. You'll get a better idea of what they mean when they're describing coffees. They'll get a better read on the sorts of coffees you're interested in.

You don't have to do all of that at once or all of it before you open your business, but get started with this in whatever capacity you can and go in knowing that this never stops. Next year's coffees will be different from this year's, farms will change what coffee varieties they're growing, change farm management practices, change post-harvest processing. You might find different markets to target with different desires and expectations. New roasting machinery can open up different approaches to roasting. The ability to taste is the ability to cut out the noise of fads and make your own product decisions.