My favorite pumpkin or squash to use for roasting is the Jarrahdale Pumpkin.
The meat of this pumpkin is similar to Butternut Squash, which is another favorite and works well with this method.
Clean the exterior of the pumpkin or squash well, making sure to remove any dirt.
Carefully cut the pumpkin or squash in half. Remove all the seeds and membranes.
Turn the oven on and set it to 400 degrees.
I like to turn the halves upside down, so the moisture within the squash kind of steams itself as it roasts.
Lay the filled bags on a flat surface, and gently press the bag from the bottom to the top, moving all the air out and flattening the puree. Than seal the bag and freeze!