You can find certified gluten-free oats, and yes you will toast them in the oven, there are other post about this. In general, oats are gluten free, though they do contain a protein called avenin which can cause a reaction in some people.
I have never seen the dried rice solids (though I haven't looked very hard), I use rice syrup.
Dry yeast is gluten-free, so use one of those. I like US-05, or T-58 might give you some more complex flavors.
Bacteria are the only culture some people have.