Ideally you should be storing the beans in a sealed bag with a CO2 valve...so for example, the type of bag you might buy already roasted beans in (if it is resealable). Otherwise, you can buy they from from Coffeesnobs quite cheaply. You can add a CS member card to your next order for free as well.
Something to keep in mind- Ive observed from my own experiences that the roast level affects the relationship between grind level, flow rate and extraction. Therefore IMO there is not too much to gain from using improperly roasted beans to say adjust your grind or practise dosing. So thats perhaps a mistake I was making when I ruined some batches and tried to use those beans to improve my technique.
Anywho your second batch looks much better than your first, and ultimately it comes down to what YOU like when you finally drink those beans. Itll take a while to get your roasting technique sorted, some will get burned and others will be under-roasted, but make sure you stick with it :)