I see he's young still, room to develop more potentially. I see his FO's aren't great, neither is his size which likely hurts his FO ability a bit. Offensively he did pretty well (I see he did PP also), how was he defensively? Who was his main wingers?
He was primarily on PP2, which also featured players like Marcus Foligno and Marcus Johansson, so not a lot to work with there.
At even strength the line combinations were pretty much in a blender most of the season. He did spend some time on the first line with Kaprizov, and was solid there, but Kaprizov himself struggled for the first half of the season. For the last few months of the season when the coach put Kaprizov-Ek-Boldy together, Rossi was stapled to Zuccarello on the second line, and that line kind of sucked, but that's generally attributed to the fact that Johansson and Zuccarello, his wingers, weren't very good even strength players last year.
For reference, Feb 7th is roughly when that Kaprizov-Ek-Boldy line was assembled. Before that he was on a 46 point pace, after that he was on a 30 point pace. I fully expect him to continue to get better. Surrounding him with actual talent will definitely help his offensive production, as his greatest asset is his brain, and he needs guys at his level or higher who can play his style.
Defensively he's solid, not great, but far from a liability. At worst he plays passable defense for a top six center.
Surprisingly, for his small stature, most of his goals come from right around the net. There's very much a resemblance of Ek's game in his willingness to go to the dirty areas, although he's still learning how to be better due to his size.
For whatever it's worth, I would much rather keep him and somehow (13th overall +) add McGroarty to the mix of Rossi, Boldy, Yurov, etc. Like the other fan you talked to, I like his game a lot and have a lot of faith in him going forward, and he would be a valuable part of the core. I just recognize that Guerin values size and, I quote, "an FU attitude", and Rossi may be moved at some point, and McGroarty is very much a Guerin style player.