Place the thinly sliced pork in a medium bowl or resealable bag. Add the wine, water, garlic, olive oil, paprika, tomato paste, vinegar, salt, black pepper, red pepper flakes or piri-piri sauce, and bay leaf. Stir well to coat the pork. Cover and refrigerate for 30 minutes; do not marinate longer than 2 hours because the thin pork can become soft from the acidic ingredients.
Set a large deep skillet over medium-high heat. Remove the pork from the marinade with tongs, letting excess liquid drip back into the bowl. Cook the pork in two batches for 1 to 2 minutes per side, just until lightly browned. Transfer each batch to a clean plate.
Pour the marinade, including the bay leaf, into the skillet. Bring it to a full boil, scraping up any browned bits. Reduce the heat to medium-low and simmer for 3 to 4 minutes.
Return all of the pork and any juices on the plate to the skillet. Simmer gently for 5 to 7 minutes, stirring occasionally, until the pork is cooked through and the sauce is lightly reduced. Remove and discard the bay leaf.
Split and lightly toast the rolls if desired. Divide the saucy pork among the rolls, spooning a little extra sauce over each portion. Add mustard, hot sauce, or pickled peppers if you like, and serve right away.