Yeah, I don't think it needs to be complicated. Valves from Weber and others seem like an unnecessary novelty. I don't get paying for them. If you're that worried about off gassing right off the roaster beans, just crack the top after a couple days.

Anyway... FWIW, I use 60ml plastic containers (https://www.amazon.com/dp/B085VX4SZP?psc=1&ref=ppx_yo2ov_dt_b_product_details) and they fit 21g of medium roast just about perfectly. My goal is to minimize air space in the container. I store in a freezer back for organization and extra barrier and toss the bag the chest freezer.