Rangnick told Bild: "We're not thinking about selling our best players this summer. There's no red line for us. We will keep our team and improve it in several positions.
"There is absolutely no pain threshold. We will keep the team - and make even more [signings] in certain positions."
Forsberg was played an instrumental role in RB Leipzig finishing in second place in Germany's top flight this season with eight goals and 19 assists.
Keita also made a huge impact from midfield, with eight goals and seven assists coming from 31 outings.