In a small bowl, combine warm broth with saffron threads. Let steep for 5 minutes to release the saffron's color and flavor.
Meanwhile, toss shrimp with olive oil, garlic, paprika, red pepper flakes, salt, and pepper in a bowl. Let marinate while you prepare the couscous.
Pour the saffron-infused broth into a medium saucepan and bring to a boil. Add a pinch of salt and the couscous. Remove from heat, cover, and let stand for 5 minutes.
While the couscous rests, heat your grill or grill pan over medium-high heat. Grill the shrimp for 2-3 minutes per side until pink and slightly charred.
Fluff the couscous with a fork and stir in olive oil, lemon zest, lemon juice, and parsley. Season with salt and pepper to taste.
Serve the grilled shrimp over the lemon saffron couscous, garnishing with extra parsley and lemon wedges if desired.