You need to go to the vet as the bird could have blunt force injuries from the rott's size alone. Also, there could be a laceration under feathers that you can't see. In the future, you're going to have to crate the puppy when your bird is at liberty. The experience was probably reinforcing for him or her. I don't know how it happened, but you have to be proactive and not put your animals in a situation where they make decisions about how to interact. I have a Dogo Argentino, which is a catch dog with prey drive. She's fine when the hyacinth or DYH are out, but I have to crate her when the queens are out: she cannot be trusted if they flutter to the floor.