Preheat the oven to 400°F.
Poke five or six holes into the spaghetti squash with a sharp knife.
Place the spaghetti squash into the oven, directly on the rack. Roast the squash until it's easily pierced with a knife, about one hour.
Remove the squash from the oven and let it cool for a few minutes. Once it's cool enough to handle, cut the squash in half length-wise, scoop out the seeds with a spoon and discard them. Use a fork to break up the remaining flesh, raking it until it takes on a stringy texture. Measure out four cups of squash for your taco filling. Save any extra for another use.
Coat the bottom of a large skillet with the oil and place it over medium-high heat. Once the oil is hot, add the onion. Cook the onion for about five minutes, until it softens and just begins to brown, stirring it constantly to prevent it from burning.
Stir in the garlic, cumin, chili powder, and smoked paprika. Stir everything up and cook the mixture for about one minute, until it becomes very fragrant.
Add the spaghetti squash and barbecue sauce to the skillet. Cook the mixture for one to two minutes, stirring constantly to incorporate the sauce into the spaghetti squash.
Remove the skillet from heat and stir in the lime juice, salt and cilantro.
To assemble the tacos, spread a thin layer of refried beans on each tortilla, then stuff it with spaghetti squash filling and any additional toppings of choice.
Serve.