So, my guess is that off-days when they don’t have games they’ll roll with a 21-man roster, when/if everyone is healthy.
They might do a 20-man roster too, but I’m assuming that they’re not going to waive any vets, and that the KHL UFA’s (Lehtonen & Barabanov) will be full-time members of that roster. The Leafs make a point of taking care of the guys they lure from overseas, and I don’t think either would be happy with getting paid a pro-rated $92.5K AHL salary while stashed on the taxi squad.
So, the full-time 21-man roster:
Auston Matthews
William Nylander
Mitch Marner
John Tavares
Zach Hyman
Alex Kerfoot
Ilya Mikheyev
Joe Thornton
Wayne Simmonds
Jimmy Vesey
Jason Spezza
Alexander Barabanov
Morgan Rielly
Jake Muzzin
TJ Brodie
Justin Holl
Travis Dermott
Mikko Lehtonen
Zach Bogosian
Frederik Andersen
Jack Campbell
And the taxi squad:
Pierre Engvall (waiver exempt)
Nick Robertson (waiver exempt)
Joey Anderson (waiver exempt)
Travis Boyd
Rasmus Sandin (waiver exempt)
Martin Marincin (

)
Aaron Dell
...and with the exception of Dell, Marincin (God, I hope so) and maybe Boyd, I expect all of these guys will get rotated on to the regular roster to get them into games with some regularity.