I might be too late for the party, but vegetable broth would do it justice. Chicken broth, not so much...beef, don't think I'd try that route.
Just remember, the temperature of your broth can continue cooking the loin, so if you want 140 or 145* finished temp, then your broth can't go above your desired finished temp or it will over-cook the loin. Roaster ovens are a bit of a PITA for reheating or holding food at temp because most everyone of them i know of heats from the sides instead the bottom. It can create a difficult situation, unless a lot of liquid is present.
BTW, folks think that if meat is swimming in liquid that it won't dry out internally. As long as temperatures are carefully controlled and maintained at no higher than your desired finished temp (never hold hot foods below 140*F for us back-yarders, or 135*F per US Food Code), then, the meat will not dry out. Temps are everything.