Put the pork tenderloins, mustard, rosemary, and salt into a gallon sized sous vide bag. Mix around the pork and the seasonings until they are coated evenly. Seal the bag using the vacuum sealer.
Add the vacuum sealed pork tenderloins to the water bath. Cook for 4 hours.
Preheat a large skillet to medium-high heat and add the olive oil. Remove the sous-vide bag from the water bath. Cut open the sous-vide bag and add the pork to the hot skillet. Save the cooking liquid. Sear the pork, turning every few minutes, until browned. Remove from the skillet and let rest for 5 minutes.
Add the cooking liquid to the skillet. Deglaze the pan and simmer until the sauce is reduced by half. Serve the pan sauce with the pork.