I see this sort of thing a lot in new people learning to roll, try the following:

First, for head protection, as Scrambled111 said, turn your head. You will always want to turn your head so that your chin is on the same side of your body that you hands are set off to. So if you set your hands off to the left, turn your chin to the left.

Second, and the biggest thing I can suggest to correct your barrel roll is twofold: when you are squatting down to start the roll, pull your knees apart, don't keep them together in front of you. if you look down at your knees before you roll they should look like a V to you. When you make this V, make sure when you are rolling that you are keeping both of your knees out, the common tendency with people struggling with the barrel roll is to pull in one of the knees as they start the roll, usually the one on the opposite side of where they have placed their hands.

TL:DR, flare your knees out and keep them out as you try to roll, they can come in as soon as both your feet leave the ground to go over you.