I dehydrate some of my roasted green chilies to use as a spice in some of my foods and to make chili powder with.
Here is how to dehydrate roasted green chili. First, start with some roasted green chili.
Cut them into 2 to 3-inch pieces 
and place on your drying trays.
Place in the dehydrator and dry for about 12 to 18 hours at 120 degrees until hard and brittle. They do shrink down a lot.
After they are dried you put them in a blender to make a powder out of them. Or you can leave them in pieces to use in recipes calling for chilis.
 You can also use a coffee grinder. You need to stir them to move them around while you are powdering them. Be sure to let it sit a couple of minutes to let the dust settle before you open, a face full of powdered pepper is not a good thing. Don’t ask how I know 🙂 .  I tried a food processor to powder them but it would not powder them.
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I put the powder into a pint jar when done. If you don’t powder just put the pieces in a jar to use as needed.
Be careful when using it is very strong a little will go a long way.
I have done the same with all sorts of Peppers.
My Favorite??? Jalapeno Peppers, Talk about SPICY!!!