Yakupov: pace of 16 goals and 36 points per 82 games with the Oilers, was a former #1 overall pick, traded for a conditional 3rd and a throw-in player
Perlini: pace of 19 goals and 30 points per 82 games with the Coyotes and Hawks, was a former #12 overall pick, traded for a 3rd
Milano: pace of 14 goals and 30 points per 82 games with the Jackets, was a former #16 overall pick, traded for a rental 3rd liner having a bad year
Fabbri: pace of 16 goals and 37 points per 82 games with the Blues, was a former #21 overall pick, traded for a 4th liner
Baertschi: pace of 10 goals and 35 points per 82 games with the Flames, was a former #13 overall pick, traded for a 2nd
Roslovic: pace of 12 goals and 31 points per 82 games with the Jets, was a former #25 pick
You can convince me that a late 2nd for Roslovic is fair, but that's about the max I'd be willing to say is fair based on precedent. There are scores of comparable players to Roslovic, whether you want to look at exact comparable (like the 5 I mentioned above) or even just remote comparables (like comparing him to Nathan Beaulieu, who was traded for a 3rd after 3 seasons of being a good bottom pair D), that suggest his return is in the 2nd-3rd range than anything higher than that.