You have to be careful when assessing the 2015 line. They didn't play together long. After Lowry and Perreault went down it was Apples with Wheeler-Ehlers, and Copp centering Roslovic-Harkins. To Maurice's credit he played Harkins over Bourque, which is not an endorsement for Bourque, but we had a 4th line of Bourque-Shore-Shaw for a good (or mediocre) month.
The 2015 line had 2 good games against Chicago and a L.A team that was in the midst of trading all UFAs and their starting goalie (with Quick out). Had a good but pointless game against Ottawa, so 3 non playoff teams they played well. Got scored against vs. Philly in a game we lost. Eakin was acquired before the Buffalo game, and at one point Harkins was promoted, to generate a goal with Scheifele-Wheeler. By the Washington back to back Eakin was centering Ehlers-Laine, which was going pretty good, and a player like Appleton was moved down to a more suitable 4th line role, over Shaw. Perreault came back to replace Bourque. Lowry came back and took Harkins out of the lineup. Each change continued our winning or point earning ways, minus the Oiler game that Laine sat out.
Lowry is going to get more minutes at centre than Roslovic. And if not Lowry than Copp will. Harkins-Lowry-Roslovic was good line against Calgary in the playins. Hard to say it wouldn't be a better line with Copp instead of Harkins. There's a lot of different line combos that can shake out of the bottom 6. Some can make the team more of a 4 line oriented attack, but Harkins and Appleton are yet to prove they are bigger scorers at the NHL level than Lowry-Copp. If I were a betting man, I would say that Harkins and Appleton still have to prove they can be regular top 9 players, but they will get some looks. Roslovic may play some centre, but I think he is more likely to be a RW, as the RW depth on the Jets is still thin. As it stands he's an injury away from being a top 6 replacement.
I like the Laine and beer reference. Sometimes Laine is a full beer's worth, sometimes Laine gives half a beer's worth, or looks like spilled beer out there. This year might be his final beer with the Jets.