Buffalo doesn;t want random prospects and picks. they would want players back. buffalo are trying to get out of the rebuilding phase, not go back in it.

We don't need a goaltender, we have Ullmark and we sign Hutton.

If youre offering goalie prospects, the sabres center you are looking for is zemgus girgensons.

According to Lebrunn, they want a 1st, 2nd, and very good prospect. Haven't seen anything about them wanting roster players specifically.
They aren't getting that before they pay his signing bonus, because the price will be the same after they pay it. Right now, they need to decide if they want to pay $7.5M and hope a suitable deal comes along later, or they can take the best offer on the table now, which would probably replace one of those pieces with a roster player that has a $3-4M cap hit.

I don't think Lindgren is the guy they would want either, fwiw.