There was a comparison to him and Roslovic and I think that's a good one. Both played their first full season in the A at D+2. Roslovic split his time D+3 between Moose, as a C on a line with Petan and Appleton, and the Jets at RW with Little and Perreault mostly, including 10 playoff games.
Getting to the NHL as a winger has fast tracked a few players, most recently Perfetti.
If the Jets are serious about making Lambert a 2C who competes against elite centres in the league, I think there are all kinds of factors to consider: physical maturity first, conditioning, roles (do you want him to work on faceoffs, PK, all the things a good 2C should do? Two way game), and I suppose there is the confidence thing too. You want your young players to succeed...putting them in situations where they may not be able to can adversely affect a player's development. I feel like he's potentially ready for the NHL but I am not sure he's ready to be an NHL 2C. The one thing to consider though is he may not get the mentorship at the NHL level from the same group of players that he could this year...
Really can't say how the organization sees him going into this year, but the last time the Jets had a centre on the team in their d+3 was Andrew Copp, who was already in his first college year when drafted, with a July birthday that separated him by one draft year from Trouba. And that was as a 4C mostly.