I would think that a pumpkin souffle using roasted pumpkin from the fridge or freezer would be so tricky, because the moisture level varies so much from pumpkin to pumpkin. I've never tried to make one, however. It's just a gut feeling, based on personal experience of having roasted dozens of pumpkins and similar squashes over the years . . . . . ;o)

Here's one from a blogger called Sugarlaws. Looks pretty simple.
http://www.sugarlaws.com/pumpkin-souffle