Honestly, it took me a minute to realize that the overlap between French and English is actually smaller than I thought (and much smaller than between English and German). I had a hard time coming up with sticky analogies for the spelling of "roulette".
Here's a memory hook:
- "ou" because that's french for "oo", as in: douche.
- "l" since it comes from "roule" or "rouler", as in: joule, boule (there is no "ll" between "ou" and "e" in french, ever).
- "tt" since it's a female noun, as in: cassette, baguette, couchette.