Good thought - I want my BP to be as healthy as possible too but as it turns out feeding the snake vitamins runs you the risk of giving to many. Snakes are designed to use as much of their prey as possible and unless ill or vet recommended do fine with good healthy rodents. F/t have less of a chance of carrying parasites.
The best way to make sure your snake is getting the proper nutrition is to feed them the healthiest prey items you can. The ideal way to do this is to raise your own so you can control exactly what they eat. But most people's snakes do perfectly fine on store-bought or internet-bought rodents, with absolutely no need for additional supplements.