I don't think there is very much of a relationship between crema production in espresso making and the roast level.

I was recently sent some samples of coffee from a professional roaster. They were so darkly roasted that I would instead call them "incinerated" rather than "darkly roasted." There were also a lot of roasting defects such as divots on a large percentage of the beans. The couple of shots I pulled on them were absolutely gorgeous, with abundant crema and the sort of shot appearance through a bottomless PF that you could have videoed and posted on the internet as being an example of sterling barista technique.

Nonetheless, the espresso was atrocious, absolutely undrinkable. I spat all of my tastes down the sink. And, when I served more of this coffee to a friend later that day, a friend who knows a good shot from a poor one, he looked like he was about to vomit a few seconds after the first taste of the shot touched his lips.

People make too much of the importance of crema. A reasonable amount of crema is going to be present in any good shot, however the presence of it is merely a necessary but not sufficient condition for having produced a good shot of espresso.

ken

farmroast wrote:Geeez Ken did you warn your friend?

Not exactly. The coffee was sent to me by a restaurateur who uses this coffee in his restaurant and who (apparently) thought he would impress me with its quality by expressing me a couple of pounds worth of samples. What I said to my friend was, "this is a micro roasted coffee from a roaster who provides coffee to high end restaurants; what do you think of it?"

I didn't want to bias him by saying that I though it tasted like an exploded tree from the middle of a raging forest fire, so, I let him draw his own conclusions