I've seen Nolan Vesey play numerous times in HS, summer and USPHL. He's good, has some skill, but not as willing to go to the net as his older brother. His dad is Merrimack's all-time leading scorer, played briefly in NHL. Brother picked by Nashville 2nd rd so there are some good bloodlines. As of now he's more of a perimeter player, but he's got some moves.
Liam Pecararo is small, but very crafty. He can really dangle. He's not going to out-physical opposing defensemen, but he'll bounce around from side-to-side and make some D look silly. I've only seen him live a couple times, seen him on FAST Hockey (stream) a few more times.
Malcolm Hayes and Mark Hamilton are similar players. Both are big, strong, physical defensemen. My personal opinion is Hamilton is more refined, but Hayes has more upside and has potential to really blossom under the tutelage of Leach and Gendron. I've only seen Hayes a few times, but I've heard good things about him from guys on campus right now who've seen him in informal on-ice workouts. I've watched Hamilton a few more times in prep and high school. He's steady, solid, nothing flashy.
I haven't seen enough of the other guys to really comment, but I'd say the four above-mentioned players are head-and-shoulders above the other rookies. Lacroix could add some physicality, be a good 4th line grinder from what I've heard. Musil is a shot in the dark in my opinion. If he works out great, if he doesn't, no scholarship $ wasted. Romeo had some potential when he was younger, but I think Morris will need to play 60% of the games to really give Maine a fighting chance.