Atsushi Kousaka(髙坂 篤志) would be continuing to do Prussia's voice in the anime(yes,
He's actually been anticipated by Himaruya-sensei to become Prussia's VA. And further more, he's also going to be doing Greece's VA in the second season of the anime.
Three roles? Wow. Prussia would be appearing again next week in the anime, btw....
Lol, Prussia and Greece has already been added in his Japanese wiki page. That's quick.
Source: Monthly Comic BiRZ