If you vacuum seal and store at room temperature, the bag will puff up from CO2 because it has nowhere to escape to. The coffee continues to outgas slowly at room temperature, even if you let them degas for 3 or 4 days before bagging. You need bags with the one-way air valve like you find in all the pre-packaged whole and ground beans that are sealed in Mylar. The ones sealed in paper don't need air valves, since they aren't air-tight.
Freezing the roasted beans will tremendously slow down the aging of the beans, and the release of CO2. The colder the better, and you don't need air-valves. In fact, if you use bags with air valves, put a piece of tape over it to seal it before you freeze it. You can vacuum bag, but coffee does just fine frozen in mason jars too.
You can for sure go 6 months frozen without a problem, meaning that you won't be able to tell after thawing that they were frozen. I just tried some I froze back in August (9 months ago), and they were as good as they were when I froze them. If you have a manual defrost type deep freeze, you can possibly go even longer.