Home Roasting with Fresh Roast SR500 I've just purchased a Fresh Roast SR500 home roaster. I have no experience roasting coffee so I'm looking for some basic principles to guide my efforts. After two batches so far, the first, done according to the directions, was horribly undrinkable, and the second, while drinkable still wasn't very good.  The flavor is a somewhat bitter aftertaste. The coffee is described as a wet processed fruity Java bean. I have so many questions I'm not really sure where to begin. 

After watching several YouTube videos it seems like every one is different. A professional roasters site advised the roasting time should be between 10 and 15 minutes for all roast levels. But that still leaves the question of how much heat and how to adjust that during the roast. 

Are there any straightforward principles for how to adjust the roast in respone to the taste I've gotten from my first attempts?  Or any guidance on differences in roasting light vs Full City which would be the darkest I would do?  

I really don't want to reinvent the wheel here and waste a bunch of coffee beans in the process.
There is a goodish guide for your roaster here.

I'd also keep in mind that coffee has a cooling period after you "stop" roasting, where it will generally still roast to a darker level (or two). You need to try to finish your roast at a level or so lighter than what you are aiming for and let the coffee "cool" into your desired roast.

I might suggest that you roast at a lower level (lower heat) so that the beans move through the stages more slowly.  This will badly suck up your time, but will also allow you greater chance of stopping the roast at the roast level you are aiming for.

Keep in mind that many of the descriptions you read for green coffee are done by people with extremely refined palates.  No matter what coffee you roast, those fruit type descriptions are still hints and notes in the coffee, not it's overall flavor.  Additionally the quality of the green beans you are roasting will affect the final quality of your roast. It's impossible to make poor green beans great by perfectly roasting them.  You can, however, ruin high quality green beans with a poor roast.  

When I started roasting, I was "lucky" enough to start with a cheap air popper.  The advantage of that is that with a popper it is very easy to hear the "cracks" associated with roasting.  My personal opinion is that the "cracks" are one of the few constants with beans that actually consistently indicate roast level. While there are other gauges out there (darkness and smell), they can vary with different varieties of beans.  Eventually I moved to a machine where I couldn't hear the cracking at all, but by then, I had learned enough of the other cues that it didn't matter as much.