Don't know if people are aware of this, but you can't draft a prospect such as Brayden Schenn in the NHL draft and put him on your prospect roster. The only way to have a player on your prospect roster is via the prospect draft.
For the prospect draft, a prospect is anyone that's under the age of 25 and has 41 or less games played as a skater and 30 or less games played as a goalie.
For this draft though, the NHL draft, you can draft prospects if you want. However, since this is the NHL draft, if you draft a prospect in this draft then he will have to be on your NHL roster. Which means that you better damn well hope he plays next season otherwise you're wasting a roster spot on him.
So, for instance, if you think Brayden Schenn is going to play next season then feel free to draft him. Just know that you're taking a risk though.
The only limit on who you can draft for this draft is that no 2011 draftees, such as Ryan Nugent Hopkins or Larsson, are allowed to be picked.