If you have a morning to spare, you can go to South Lake Union area and these cafes who roast their own beans are all within a 1 mile radius.
Cafe Vita
Caffe Ladro
Elm Coffee Roasters
Herkimer Coffee
Zoka Coffee

I know for sure Ladro, Herkimer, and Zoka have multiple roasts ready to pull espresso. Also within that area is Fresh Flours (serving Stumptown) which sells a selection of beans from multiple roasters.

I drink lattes but when trying a new roaster for the first time who happens to have a storefront, I frequently order an espresso shot so I have a baseline taste before I try it at home. All that being said, the barista at home makes espresso that matches your particular preferences whereas the cafes serve what they think matches the general public's preference.

I'll second Lighthouse roasters. It's our go to roaster; great beans and it's a special treat if the roaster is running.

Vivace is a great recommendation as well, it's a Seattle tradition.

I love Vivace but also really like Victrola coffee there. Lots of great options in Seattle.

My favorites are Vivace and Herkimer for sweet classic espresso. Both shops do ristrettos with 17-18 grams in and a similar amount out. For Vivace Dolce beans and on a Niche zero you want to aim for a 1:1 ratio or about an ounce of liquid in 27 or up to 35 seconds (at least that's what they use at their shop), brewed at 203 degrees.

Victrola is also good, but they aren't as dark. Ladro and vita make beans like you want, but their caffes are very hit or miss with drinks sometimes coming out worse than Starbucks.

Union Coffee in Seattle serves Looking Homeward coffees... my current favorite espresso beans.

Victrola Streamline has been good every time I've tried it; the one spro I had at Herkimers was very bad - under extracted, sour thing. It put me off, but I do walk by there several times a week, I'll give it another go.

Just got back from Seattle yesterday and had espresso at Vivace and bought a bag of Dolce Decaf. Saw the 3 modified Niche Zero grinders with bean hoppers. Been going there for years when in the Seattle area (the store on Broadway)

Yes, they've had the Niche's for a while now. I last visited in December of 2020. The barista showed the slight modifications as they are hooked up to some type of control box so they can just run and don't have to worry about flipping the grinding on and off. Testament to how reliable the Niche's are as Dave Schomer the owner of Vivace hasn't changed his grinders in years despite them being discontinued from production for many years so it's a big deal when he changes something. Page 2 of the Vivace blog talks about the Niche.