What affects to taste balance and texture of the espresso
In terms of extraction, the taste balance is decided by the brew ratio. This is a very important point to understand how roasting affects the taste balance. Simply, the more the beverage yield the coffee is extracted, the more bitterness is contained in the cup. Also, the higher the roasting degree, the more the bitterness. This can be interpreted as that the higher the roasting degree, the smaller the beverage yield, and vice versa.
For the texture, the higher the roasting degree, the heavier the weight of the body and the bolder the texture. So, when extracting a lightly roasted coffee, (it depends on the details in roasting profile, but simply saying,) it might be good to grind the coffee finer in order to get a bolder texture, and it might be good to grind the coffee coarser in order to get more pleasant and silky texture if the coffee is a dark roast.
Intensity and Roasting Time
As described, the roasting degree affects the taste balance and the texture of the coffee. And there is another part that affect the quality of coffee, which is roasting time.
Roasting time affects the intensity of coffee in various forms. For example, for short time roasting, it enhances the intensity of the aromas and flavours. And when the coffee is roasted for a long time period, the intensity becomes weaker, but highlighting the sweetness and the body of the coffee.
How can we know how the coffee is roasted?
By looking at the colour of the bean, you can get some insights how the coffee is roasted. The lighter the outside of the bean, the lighter the coffee is roasted. And the bigger colour gap between the whole and the ground, the shorter the roasting time is.
So, by checking the colour of the bean, you will be able to know how the coffee is roasted and how you approach to extract the coffee.