It's well-known in Mexico that they are antiparasitic and in fact, most people around where I live grow winter squash, especially for the seeds. They cut them open remove the seeds, then toss the flesh to the cows. The kind like you pictured you can easily eat the shells, it helps get some extra fiber in you too to help move those intestinal parasites out. One trick for mas shelling them--before roasting (for example there is a lovely green sauce called pipian made with ground pumpkin seed, is the following.
1, soak in water to wash and remove pumpkin pulp.
2, crush them gently with a rolling pin--not hard
enough to crush the insides.
3, boil for just a minute or two
4, cool and strain
5, peel and leave to dry
You can also toast them this way, you will often find them peeled in Mexican peanut snack mixes.