Isnt boxed roux sacrilegious to a Louisiana native? I'd think it akin to par-boiling ribs before they hit the smoker in these parts... Effective, but not the Way Things Are Done. Oh, don't get me wrong... I could see where a box of Zatarain's would improve the efforts of an Toddowen, AP, or some other culinary pinhead, but from the looks of your PET, you'd already gone to a buncha trouble, so what's another 45 minutes?
That said, it's hard to beat Zatarain's for most anything they make, as I've been known to reach for a box of their red beans and rice of a mid-week evening when I don't have 3-5 hours to fix the Genuine Article.
I don't have the luxury of a gas range, and I can imagine where this might be the case. There ain't no saving a burnt roux. A big-ass non-stick pot and about 30 minutes of elbow grease usually produces the chocolately-thick base I'm looking for to brew my gumbo....rouxs can be tricky, they are easy to burn...
Never tried your chicken and sausage version; we eat jambalaya every week-or-so, and I always figured it to be redundant. We like to do a seafood gumbo when I can find fresh oysters - which is a rare occasion, sadly, in these parts.
Still, that looks like a fine mess of good eats, JSC, and I thank you for posting it! Can't wait to give it a try when the okra come in season this spring!