Going through some of the official rosters and some interesting (or not so interesting, depending on your POV) facts on each team
ANA: Ducks have 5 (Jack Badini, Bryce Kindopp, Roman Durny, Maxim Golod and Olle Eriksson Ek) playing in the ECHL but of those 5, only Eriksson Ek earned an invite to camp.
BUF: Sabres signed two NCAA UFAs last Spring but only invited Brandon Biro to camp, leaving Dawson DiPietro to await the possible open of the AHL season to get some practice in.
DAL: Despite the NHL allowing an unlimited amount of goalies to come to camp, the Stars only brought the 4 under contract to camp (5 if you include the injured Ben Bishop).
DET; Wings left some notable players off their roster to continue playing in Europe (Joe Veleno, Moritz Seider) but the most unusual is Calvin Pickard (Who is playing in Austria) who is on a 1-way deal with the Wings.
LAK: The most interesting inclusion is D Daniel Brickley who is under contract to the Kings but was dealt at the AHL level last year to WPG's AHL deal before the end of the season.
MTL: Habs left some notable prospects off the roster, like Cameron Hillis and Josh Brook (The latter being a 2nd round pick in 2017).
PIT: Was a little surprise to see that the Pens left Will Reilly off he roster when they just signed him less than a year ago, ditto for Jonathan Gruden who was acquired in the Matt Murray deal. Despite having an ECHL agreement with Wheeling, the Penguins have not assigned any of the 4 signed North American prospects to the Nailers (Reilly, Gruden, Justin Almeida and Jordy Bellerive).