Does he have the right to do give others permission to come here to hunt?

The answer to this question would be contained in your lease agreement with the landlord. If he is just renting the home to you and not the land, then he still has a right to do so. There would however be the violation of quite enjoyment of the premises due to the hunters being allowed on the property. I would have to see the original lease agreement to advise you further.

I suppose you have the right to lock the gate, but the roommate has the same right to open it. Does the lease prohibit hunting? Does the landlord prohibit hunting? If not, then I suppose that if you are both on the lease, one of you can permit hunting on the property.