Boil the rice until cooked, then drain.
Meanwhile, heat the oil in a large frying pan, and add the diced tomatoes. Cook for a few minutes until soft.
Transfer the drained rice to a large bowl, along with the cooked tomatoes, smoked paprika, ground cumin, sriracha, and plenty of salt and pepper.
Heat a bit more oil in another large frying pan, and add the mushrooms and garlic. Cook over a medium heat until the mushrooms are soft and most of the excess liquid has cooked off.
To assemble the burritos, lay a tortilla wrap out on a square of tin foil that’s just a couple of inches larger than the tortilla itself. Add about 3 heaped tbsp of the rice mixture along the centre, followed by a couple of tbsp of black beans and a couple of tbsp of mushrooms. Top with some grated cheese and chopped coriander. Roll the burrito tightly, tucking in each end, then wrap tightly in foil.
Cook in the oven at 190°C (Gas Mark 5 / 375°F) for around 20 minutes, then serve.
Alternatively, before cooking, freeze until needed.