I like to roast quite light, but I often find that the roasted beans come out very dense and hard — so much so that it sometimes stalls my grinder. Also when brewing as espresso, I have to grind really fine and it still often comes out quite fast with a fair amount of channelling. Some beans have this issue much more than others (e.g. I’ve noticed it a lot with a washed Peru and washed Guatemala that I’ve had).
The workaround I’ve been using is to roast a little darker than I’d like (usually a slightly longer dev time which results in a slightly higher weight loss).
I’d like to know if there are any techniques for increasing solubility/porosity and reducing density, without ending up with a darker roast?
For reference, I’m roasting on the R2 Pro and usually roast full 1.2kg batches. Typical weight loss is between about 11.5%–13% (depending on the bean).
Here’s a typical example roast (this is a washed Peru):
Here’s a quick answer. I don’t know what type of grinder you’re using, but you might want to consider getting something else. I say this as someone who usually roasts light, and my grinder, even the smallest one, never stalled. The small one is the Eureka Mignon.
As for espresso, you’ll have to deal with the channeling. Espresso machines are not made for extracting light roasts cleanly. The thing you’re after is the taste. Once you find that, it doesn’t matter how your shot pulling looks like and if there’s channeling. You could try to “distribute” your grinds with a toothpick or some other tool, but that won’t help much.
As for roasting, you’ve pretty much nailed it. You could play with balancing out the drying and the Maillard, but that won’t really make too much difference. Try and see. Also, the graph here looks more like something close to a medium roast. I drop many of my beans during FC, with max development at around 10%. But I do like experimenting and changing profiles constantly. You’ll often hear roasters talking about “espresso roast”, which is to say “we roast darker”. There’s no such thing as a specific espresso roast. The grinder is what determines the type of preparation. Roasting darker usually happens in commercial environments where people need consistency, something like fast food, to be able to pull many shots that are all the same. You don’t need to do that. You may concentrate on taste alone. Forget the channeling and pretty shots, ratios, etc. Look for taste.
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Thanks for the reply. I do use a WDT tool for my espresso puck prep, and I’m using a Niche Zero for my espresso grinding — I think the issue is that it’s a low RPM grinder so can’t handle very dense beans. Still, I have ground some very light roasts from some other roasters and it’s been fine, so I’d like to think there’s something that can be done. Although it could just have been that particular bean or something to do with the particular roaster that was used 
This really sounds very strange. I’ve had grinders stalling, or grinding to a halt (pun intended), but that was only with darker roasts and finer grind settings. The reason was that the grounds weren’t exiting the chamber, or the burrs if you prefer, because the setting was too fine and that led to the blockage and the stalling. I doubt that RPM speed has anything to do with it. If a hand grinder crushes the beans at 2 RPM, so should any electrical grinder. Maybe you should, if you haven’t already, inspect the burrs for damage and allignement. I don’t have any other ideas.
