Really. I'm not too worried about a 20 year-old not playing in the NHL, especially if he's smaller-framed and needs to fill out just for the AHL/NA ice surface, or could still be acclimatizing to living in the States. Specifically for Östlund, he has missed 20 games this season and I don't know if he was playing through anythingbefore it or if he's had a consistent line and role on the team as a result of the injury. I also wouldn't have picked Östlund; I had him behind Kulich, Ohgren, Miroshnichenko, probably even Yurov, especially since they had just drafted another small-framed guy in Savoie.
Rosén, I agree, but for him it's more that he's shown me nothing in the NHL, not even a glimmer. (Now, Kulich also didn't show much in his first handful of NHL games, either, but he did have a great shot as his calling card and he really did look solid in camp when he couldn't be taken off the puck.) Armia is a good comp, and honestly, getting a bottom 6 forward after the 15th pick is fine (though, I'd rather have Kucherov from that draft).
And I do agree, Helenius has a future in the NHL. Will either of them be with the Sabres? Too soon to say.