Emily, any guidance on how I would adapt this recipe for a low, slow cook in a tangine/dutch oven version?

Personally I would seek out authentic and traditional tagine recipes from Paula Wolfert (or another reputable source) rather than try to back-engineer a contemporary "school night" sheet-pan hack.

This recipe is roasting which is an entirely different cooking method than braising so the end result from a tagine will look vastly different than what is pictured here.