Place an oven rack in the center of the oven, then preheat to 450°F. Wash and dry the fresh produce. Line a sheet pan with foil. Medium dice the potatoes; place on the sheet pan. Drizzle with olive oil and season with salt, pepper, and half the spice blend (you will have extra). Toss to coat; arrange in an even layer. Roast 18 to 22 minutes, or until browned and tender when pierced with a fork. Remove from the oven. 

Meanwhile, halve, peel, and thinly slice the onion. Cut off and discard the stem of the pepper. Quarter lengthwise; remove the ribs and seeds, then thinly slice crosswise. Peel and roughly chop 2 cloves of garlic. Slice the chives into 1/2-inch pieces.

In a medium pan (nonstick, if you have one), heat 2 teaspoons of olive oil on medium-high until hot. Add the sliced onion; season with salt and pepper. Cook, stirring occasionally, 3 to 4 minutes, or until lightly browned. Add the sliced pepper. Cook, stirring occasionally, 3 to 4 minutes, or until slightly softened. Add the vinegar (carefully, as the liquid may splatter). Cook, stirring occasionally, 30 seconds to 1 minute, or until the liquid has cooked off. Transfer to a large bowl; cover with foil to keep warm. Rinse and wipe out the pan. 

Pat the shrimp dry with paper towels; season with salt and pepper. In the same pan, heat the butter on medium-high until melted. Add the seasoned shrimp in an even layer. Cook, without stirring, 2 to 3 minutes, or until slightly opaque. Add the chopped garlic. Cook, stirring occasionally, 1 to 2 minutes, or until the shrimp are opaque and cooked through. Turn off the heat. 

Add the roasted potatoes to the bowl of cooked vegetables; stir to combine. Taste, then season with salt and pepper if desired. Serve the finished vegetables topped with the cooked shrimp and sliced chives. Enjoy!