After some research, I discovered that real galette crust has lots of butter involved, thereby keeping it from becoming hardtack. This recipe tries to use baking powder as a leavening agent instead, but it just doesn't work. I don't know why the dough is supposed to be refrigerated for 30 minutes - it's not a terribly sticky or proteinaceous dough (mine was actually quite dry), and by the time you roll it out 30+ minutes later any leavening provided by the baking powder is already exhausted. There's no point to adding baking powder to a dough if you're not going to cook it immediately. You'll just get a brick like I did.
And then there's the top-level highlighted review that says feta is an ok substitution for the chevre. Since that's what I had on hand, I used it. However, between the salty olives and the large amount of cheese in this recipe, feta is a BAD idea. The vegetables and rosemary have a lovely delicate flavor that is just steamrolled by the feta but would probably be enhanced by chevre.
Which brings me to the good part of the recipe - roasted parsnips, beets, and carrots. Heavenly. And rosemary is the perfect accompaniment to these sweet earthy veggies. All that sweet goes well with the salt of the olives. But not with hardtack, unfortunately.
Again on the downside - I'm not really feeling these recipes that are technically vegetarian but don't really have a complete protein (cheese notwithstanding). It ends up being just a side dish when it comes to being satisfying. Ended up eating some leftover polenta to complement the wheat protein.
If I were to do it again, I'd either roll and bake the dough immediately after mixing or I'd use a real galette crust recipe. I'd use goat cheese, and not substitute with feta. And I'd definitely do as much as possible ahead of time because this is one long involved recipe.